The Bioacoustics of Tabanidae (Diptera)

THE BIOACOUSTICS OF TABANIDAE (DIPTERA)

DISSERTATION

Presented in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in the Graduate School of The Ohio State University

By Bastiaan Meijer Drees. B.A., M.S.

* * * * *

The Ohio State University 1980

Reading Committee: Approved By Dr. Donald E. Johnston Dr. Glen R. Needham Dr. Donald J. Borror ACKNOWLEDGEMENTS

This investigation could not have been undertaken without the help and support of many individuals. I am deeply grateful to my adviser, Professor Donald E. Johnston, for encouragement and guidance throughout my studies, and to my father, Mr. Jan Meijer Drees, for providing technical assistance for the aerodynamic aspects of insect flight. I am also indebted to Professor Donald J. Borror for the time and effort he gave in teaching me the fundamentals and techniques of bioacoustics, and to Dr. l. L. Pechuman of Cornell University for his continued assistance with the difficult dipterous family, Tabanidae. Special thanks must also be given to Professor linda Butler of West Virginia University for giYing me a broad base of entomological knowledge and the enthusiasm to pursue my interests. I have enjoyed working with my examination committee members, Dr. Glen R. Needham and Professor Willard C. Myser and I thank them for undertaking a project which was slightly out of the ordinary. Other members of The Ohio State University faculty who have had a profound influence on my years as a doctorate candidate include, Or. D. J. Horn, Dr . G. Ekis, Dr. D. L. Denlinger, Dr. C. A. Triplehorn, Dr. G. W. Wharton, Dr. W. A. Foster and Dr. W. C. Rothenbuhler. Day to day

ii existence in Columbus, Ohio was possible and even enjoyable only because of the close friendships and support of my fellow graduate students including Dr. Dan Potter, Dr . Jay Bradfield, Beth Lenoble, Maury Walsh, Greg Walker, Lucille Antony, Connie Rogers, Larry Ross, Ann Gnagey, and Rick Helmich. Finally, I wish to thank the two women in my life: my mother, Jacoba Meijer Drees, and my wife-to-be, Carol Frost, to whom this work is dedicated .

iii VITA

June 28, 1952 Born, Amsterdam, Netherlands 1974 B.A., Biology with minors in Chemistry and Art, West Virginia University, Morgantown, wv. 1974-1976 • • . • • • • • • laboratory Technician, curator of the Rhopalocera and Tabanidae sections of the Insect Museum, and application of green house pest control in the Horticulture Greenhouse for the Department of Entomology, West Virginia University, Morgantown, WV. 1975-1976 . • • • • • • . • Insect Specialist, identifications and control recommendations, assisting Or. J. F. 8aniecld, West Virginia Cooperative Extension Service, West Virginia University, Morgantown, WV. 1976 Andrew Delmar Hopkins Scholarship in Entomology, West Virginia University, Morgantown, WV. 1976 M.Sc., Entomology, West Virginia University, Morgantown, WV. 1977 Teaching Associate, Economic Entomology, The Ohio State University, Columbus, OH. 1977-1979 Ohio's Survey Entomologist, in cooperation with the United States Department of Agriculture, the Ohio Department of Agriculture, the Ohio Agricultural Research and Development Center, and the Ohio Cooperative Extension Service, The Ohio State University, Columbus, OH. 1979 • . • • . . • . • • • Teaching Associate, General Biology, Department of Zoology, The Ohio State University, Columbus, OH. iv 1979 Administrative Assistant and insect specialist for Dr. R. l. Miller, Ohio Cooperative Extension Service, The Ohio State University, Cc~~bus, OH. 1979-1980 ••.•.••.• Teaching Associate, Insect Morphology, Economic Entomology, and General Entomology, Department of Entomology, The Ohio State University, Columbus, OH. 1980 • • • • • . . • • • • Instructor, Biology- The World of Insects, Urban Extension and Community Programs, The Ohio State University, Columbus, OH. 1980 ••.•...•••• Ph.D., Entomology, The Ohio State University, Columbus, OH.

PUBLICATIONS Baniecki, J. F., and B. M. Drees. 1979. General leaf Feeding Caterpillars, Pest Information Series 87. Cooperative Extension Service, West V1rginia University, Morgantwon, WV. 1976. Ants and their control. Pest Information Series 95. Cooperative Extension Service, West V1rginia Unlversi~- Morgantown, WV. 1976. Fleas and their control. Pest Information Series 96. Cooperative Extension Service, West VTrgln1a University--.---- Morgantown, WV. Drees, B. M. 1977 . in The Cooperative Plant Pest Report 2(15-36). APHIS-PPQ, Unitea-states Department-or-Agriculture, Hyattsville, MD. Citations from the 1977 Ohio Cooperative Economic Insect Report (1-26) . -- --- 1978. in The Cooperative Plant Pest Report 3(16-36). APHIS PPQ, United~tates Department Of'~riculture, Hyattsville, MD. Citations from the 1978 Ohio Cooperative Economic Insect Report {1-26). - -- Drees, B. M. and l. Butler. 1978. Rhopalocera of West Virginia. J. lepidopterist's Society 32(3):1g2-206. Clement, S. L., G. Szatmari-Goodman, and B. M. Drees. 1979. The status and control of the Ohio corn rootworms. Ohio Report 64(1): 8-10. v Drees, B. H.• L. Butler, and L. L. Pechuman. In lress. The horse flies and deer flies of West Virginia; An-rl ustrated key (Diptera, Tabanidae). Biological Bulletin, West Virginia Experiment Station, West Virginia University, Morgantown. WV.

FIELDS OF STUDY Major field: Entomology Areas of Specialization: Biology of Rhopalocera and Tabanidae, insects of economic importance. and insect behavior.

vi TABLE OF CONTENTS

Page ACKNOWLEDGEMENTS ii VITA ••••• iv LIST OF TABLES ix

LIST OF FIGURES X INTRODUCTION • • literature Review of Tabanid Sexual Behavior and Rationale for Investigating the Sounds of Tabanid Flight 2 METHODS AND MATERIALS • • 11 Collection Techniques 11 Recording Techniques. • • • • • • 12 Wing Modifications or Mutilations 15 iemperature Modifications 15 Sonagrams • • . • . • . 16 loudness. • . . . . . • 17 Anatomical Measurements 17 Wet Weight • 17 Wing Slides. 18 Wing Length. 18 Chord. . • • 18 Wing Area. • 19 Wing Loading . . • • . • . • 19 Effective Aerodynamic Center 19 RESULTS AND DISCUSSION . . . . • . • • 23 Elements of Tabanid Flight Sound. 23 Temperature and Sound • . . . . • . . • • . . • . • • . • 25 The Effect of Wing Dimensions, Wet Weight and Wing Loading on Flight Sound . . . . • . • 28 Wing length. . . . . • . . . . 31 Chord. . . • ...... • 32 Wing Area ...... • . 32 Effective Aerodynamic Center . 33

vii Page

Wet Weight •••••••••• 35 Wing Loading ••••••••• 37 Loudness or Sound Intensity ..•. 41 Sexual Differences of Tabanid Sound • 42 Relation of Wing Beat Rate to Habitat 43 Concluding Remarks. 45 SUI-t!ARY. 84 APPENDIX A. Collection Data for Specmens Recorded 86 B. Flight Mode of Diptera • • • • • • • 92 C. Sample Calculation of the Effective Aerodynamic Center. 93 BIBLIOGRAPHY . • . . . • • • • • • • • • • • • • • • • • • . • • 94

viii LIST OF TABLES

Table Page 1 Observations of Tabanid "Courtship" Flights ... 6 2 Means, Standard Deviations, and Sample Sizes for the Wing Lengths, Wing Areas, Wet Weights, Wing Loads and Wing Beat Frequencies Between 26 and 2B°C for Thirty-nine Species of Tabanidae .•. 29 3 Factors Influencing the Sounds of Tabanidae (Di ptera) . • . . • • . • . • • . • • . . • . . • • 47

ix LIST OF FIGURES

Figure Page Container used for rearing field collected late instartabanid larvae • . . • . . • • • . • • • 48 2 Two dimensional modified Malaise trap baited with dry ice and a shiny black sphere for field collecting adult Tabanidae •.•.••••••.•.•.•.• 50 3 Recording chamber - top view with lid removed and leaning against one side .•.••••••••.• 52 4 Specimen holder, constructed of 1/4 in. plexiglass and 1/8 in. diam. plexiglass rods. 54 5 The outline of a tabanid wing •.•••••.••. 56 6 Chrysops cincticornis attached to the tethering rod with rubber cement, resting on the trap door •••. 58 7 Chrysoys cincticornis in typical attitude of flight after osing ground contact with the trap door ••• 58 8 Sound production • • . • • 60 9 Flight sounds of Tabanidae (Diptera) 62 10 The relationship of the wing beat frequency to hannoni cs. • • • • • • • • • • • . • • • • • • 64 11 Average wing beat rates (cps) and standard deviations calculated for 17 species of Pangoniinae • • . . • • • 66 12 Average wing beat rates (cps) and standard deviations calculated for 22 species of Tabaninae • • • . . . • . 68 13 Sonogram of Chrysops vittatus (female) showing the fundamental tone or wing beat frequency (Hz or cps) and 5 harmonic overtones • . • • . • • . . • . • • . . 70

X Figure Page 14 The effect of temperature changes on the wing beat rates of individual tabanid specimens. . . • . . • 72 15 The effect of temperature range and sample size on the presentation of results. • • . . • . . • • • • 74 16 The relationship between mean wing beat rates (Y axis) and mean wing lengths (X axis) of 12 species of Pangoniinae and 20 species of Tabaninae. . • • . 76

17 Wing beat rate and wing length relationships of Tabanidae and Culicidae, and Greenewalt's (1962) boundary line. . • . . • . . • . . • • • • . 78 18 The effect of increased wing length (X axis) on wing shape (Y axis) . . . • • • • • • . • • • 80 19 The relationship of wing length (X axis) to body weight (Y axis). . • . • . • • . . • . • 82

xi INTRODUCTION

Since Roth (1948) demonstrated conclusively that male Aedes aegypti were attracted to the sound produced by the flight of the female, bioacoustically and ethologically oriented entomologists have been searching for biological significance of the noises produced by the wing movements of other Diptera. Much work has been done with Culicidae (Costello, 1974); Wishart and Riordan, 1959), Drosophila (Williams and Gambos, 1950; Sharp et al., 1975; Bennet-Clark and Ewing, 1968 and 1970; Waldron, 1964; and Webb et al •• 1976), Tephritidae (Sharp and Webb, 1977), and Glossina (ICIPE, 1974; Popham et al., 1978). Other authors have begun to describe the sounds of related species in search of acoustical isolation or sounds which can be played back to members of the same or opposite sex to observe behavioral responses. Sounds of related species may also have some taxonomic value. Asilid flight sounds have thus been described by Lavigne and Holland (1969), and more recently the sounds of 13 species of Canadian mosquitoes have been described by Belton and Costello (1979). The objective of the research presented here is to describe the flight sounds of species of horse- and deerflies (Diptera, Tabanidae) with a consideration for the factors which influence the sounds produced.

1 2

Literature Review of Taba ni d Sexua 1 B.ehavi or and Ration a 1 efor Investigating the Sounds of Tabanid Flight The ability for an organism to perceive and respond to environ mental stimuli is essential for survival. Since "species" may be defined as an ecological, reproductively isolated unit, an important behavioral activity of members of a species is mate location leading to copulation. This is the process of sexual recognition, not to be confused with sexual isolation. Mechanisms of sexual recognition vary greatly and are not documented for the majority of existing organisms. Descriptions of the phenomenon of sexual recognition are highly desirable not only in light of the natural history of organisms, but also to facilitate the breeding of species in captivity making them available for more extensive and controlled scientific research. No one has successfully been able to induce Tabanidae to mate in captivity (Schwardt, 1932, 1936, Philip 1931; Hafez et al. 1971), although many species have been reared from egg to adult. Tabanidae are considered to be one of the more important groups of hematophagous insects for which adequate control measures have not been achieved. These facts emphasize the desirability of understanding sexual recognition mechanisms for this family. Sexual recognition may be defined as the process by which one sex recognizes and proceeds to mate with the other sex of the same species. Sexual isolation may be defined as "behavioral barriers to hybridization between species or populations" (f4anning, 1972). Both concepts always apply after evolution has progressed during a period of reproductive isolation. The concern here is only with the adults 3

of sympatric species because sexual isolation must be supported by the

evolution of highly specific signals which enable adults to ~ecognize the opposite sex of their own species. These signals are emitted by one sex and perceived by another and are responsible for the low incidence of hybridization found in natural conditions. In many insects and probably in the Tabanidae, sexual recognition is especially important for females. Males can usually mate several times in their lifetime but females mate only once (Manning, 1972). The sexual isolation and recognition mechanisms are actually genetic differences between species expressed phenotypically. When sexual recognition signals are to be employed, these signals must be produced and perceived by morphological and behavioral signal producing and receiving structures. Signal perceiving structures may involve the senses of taste, touch, smell. vision and sound. Tabanids have been shown to possess structures which can detect all of the senses except sound (Lall, 1969; Wilson, 1966; Yelizarov and Chayka, 1978; Anthony, 1960; Oldroyd, 1964; Roberts, 1971; Thornstein, 1958). Signal producing structures may stimulate one or several of the sense structures and operate in a particular sequence. Obviously, the senses of touch (tactile sense) and taste (gustatory sense) are involved when the flies are already together and therefore, cannot be responsible for the attraction of the two sexes from a distance. And, although these are probably important in the final stages of copulation, it would be a behavioral disadvantage to spend much energy to pursue and contact other species before locating a mate. Pheromones 4 may also play an important role in sexual recognition of Diptera (Cowan and Rogoff. 1968; Ubel et al .• 1975). Tabanidae rely heavily on visual clues for host detection, oviposition sites, and habitat recognition. Discrimination between shapes. sizes. light intensities. colors. and movement is probable because of the well developed compound eyes of tabanids (Philip. 1931). but whether vision alone accounts for species recognition is debatable. Tabanid species vary greatly in size. ranging from about 4 to 35 mm in length. Obviously, the male of a small species will not approach much larger species to attempt copulation. Several members of the family are very brightly colored. Hybomitra cincticornis is a striking example with its bright orange basal abdominal segments contrasting with the black coloration of the rest of the body. Coloration is especially well developed in tropical regions, where some tabanids are mimics of Hymenoptera as a result of modifications in form and color.

The shiny metallic coloration of ~ome tropical species could playa role in visual recognition between species. However. the majority of tabanid species are not brightly colored. but are rather dull and only subtly different in abdominal (Marchand, 1918), eye (Daecke, 1906), or wing patterns (Brennan. 1935). This is especially true of many sympatric species. It seems highly unlikely that these species can recognize their mates by color or shape alone, especially at a distance. Time of mating, mating habitat. flight height (Roberts. 1975) and flight velocities may be important species recognition signals which are visually perceived. 5

It is appropriate here to discuss in detail what is already known of tabanid sexual behavior, before continuing the discussion of the role of vision. Male Tabanidae have long been known to hover at certain times of the day in specific locations (Table 1). However, many authors express doubt as to whether these are in fact "courtship" flights (Oldroyd, 1964; Craig, 1944; Evans, 1966). On the other hand, there exists much literature concerning these flights and on a few occasions, matings have actually been observed during the swarming period (Table 1). If the hovering behavior of males is in fact a courting flight, mating times and locations are highly specific and may serve as a species isolating mechanism (i.e. Tabanus thoracinus and !.· insignis in the rain forests of Uganda - see Table 1). Behavior during hovering flights seems to involve territoriality while in other species, many males will hover together in a loose swarm (Bailey, 1947; 1948; Evans, 1966). With Hybomitra cincta "hovering is an individual affair and usually no more than one or two males (are) seen so engaged at the same time. On a few occasions when two or three (are) found hovering together, they (are) always some yards apart" (Bailey, 1948). Bickle (1955), in describing the hovering of Tabanus (i.e. Hybomitra) aurilimba, explains that "when another insect flew near, the fly would make a 'pass' at the intruder, return to the same location and continue to hover." Territoriality may be a necessary requirement in sound attraction because "sound responses work better if there are no other individuals to cause confusion ••• attraction of a male to a female can only occur in relative isolation and not amongst a crowd or swarm" (Haskell, 1961; from Oldroyd, 1964). TABl[ I IJbstrvatlons of Tobanld "Courtship" Flights

Flight Copulation Species OLserver Fll~ht Oates TIN of Day Heights Observed

TAbanus americanus Hnemann (1943) 9 Sept • 15 Sept 7:00 p ••• 3-5 ft. Ito --rg:lg•nteus) 30 3 ft. candles T• .lMertcanus Nagmann •t •1. 10 Aug • 12 Aug 7:20-8: 10 p.ll, 2-5 ft. Yes - {glganteus) (1947) to 20 ft. !· sulcifror:!!. Huemann (1943) 27 July - 2 Sept 5:30 . .... 30 ft. No I to 3 or 5 ft. above trees candles, 20-25 •· no courting below 60 !· sulcifror:!!. Hlne (1903) late July & before 9: DO 1 ·•· south sldl Yes through Aug of IOOOds !· !!!2lli!~ t Haddow et ol. not stoted noutlc•l tlfll~ht not stated (1961) Ug1nda 'ttl sun Is I rain forest be 1ow hortron !· lnsignis t Ha~dow et ol. not stoted nrlves 25 •ln. not stated (1961) Uganda later r•tn forest !. PhlntOP! llebb and llells not stated 8-9:00 p .• • not stated (1924) H,yboonttro ourtli.W Bllckle (1955) 6 July • 30 July 9 •••• - 5:00 , ••• 1-3 ft. Ito !!.· clncta Batley (1948) 7 July • 29 July 8:30-9:40 •••• 1-4 ft. Ito 1:30-5:10 p ••• !!.· .!.l.!.2!!. Philip (1931) ll July • 12 July 9:30 •.•. - .,.les perched Ito 12:00 noon on vegetation Chrysop• fulalnou lttcCreory ( 1940) 9June · 10June 9-10 •••• 111tlng pairs resting on aquatic vegetatt011 '" !· rel-rdtll Lavigne, Blooa 26 June • 4 Aug 7:27 .. 11:02 •••• coupling In air Yes and Heys ( 1968) fro111 3 ln. to 5 ft. high SOIOetllltS accompanied by brief hover ~· !!!!!!!.~ 13June-7AUI 7:45 .. 10:23 •••• N1es coupled lflth ~d'2..";; t:=, f-1• Ia flight '" 7

Actual mating was observed for Jabanus americanus (= giganteus) by Hagmann et al. (1948). In this case "the male struck the female and connection was made in flight, after which the pair attached to a leaf, one holding firm there while the other hung motionless below." Evidence indicates that mating appears to be proceeded by hovering of the male, who is presently joined by a female, and the pair flies off to rest on the vegetation. Lavigne et al. (1968) present the most detailed account of the mating behavior of tabanid species, and for I· rein\'1ardtii and £.. fulvaster coupling aways occurred in mid-air. However, coupling was not always preceeded by hovering. Other Tabanidae are known which do not appear to hover before mate location and copulation. Mating pairs of Chrysops fuliginosa were observed by MacCreary (1940) to "rest upon cattails and other vegetation (in the breeding area). Upon being disturbed, they would fly erratically a few yards to another resting place without separating." Hine (1903) observed a close association between ovipositing female C. moechus, males resting on vegetation, and mating. If hovering is actually a courtship behavior, undoubtedly vision is involved in detecting hovering time, location and possible mates. If hovering is not involved in courtship, vision may still be involved to detect the location, flight height (Roberts, 1S75), flight velocities and other characteristics of the opposite sex. However, it is unreasonable to assume that vision alone is involved in the process of sexual recognition. 8

The statement that "Tabanidae cannot sense sound" would be a very difficult one to defend. Never has an insect been shown not to have the capacity to react to vibrations caused by sound. The literature is repletewith citations studying the various sensory structures of insects which have enabled them to tap certain frequencies of sound (Fletcher, 1978) (Ehrman, 1959) and utilize them for prey location (Cade, 1975), to escape from predators, in establishing territories, for mate location and in sexual isolation. Many families of flies have been shown to utilize sound . Evans (1966) and others have discussed the utilization of sound in courtship behavior for Culicidae, Chironomidae, Asilidae and Drosophila. Indirect evidence and speculation that Tabanidae utilize sound communication also exists. Philip (1931) was the first to suspect acoustics in species recognition when describing the activities of Tabanus (= Hybomitra) illota males. His lengthy quote will be given here because of the importance of the details observed: The males ofT. illotus were also observed sitting about on grass and leaves exposed to the sun and generally over shallow standing water. They were seen to dart up as if chasing something and then return to the same or a neighboring leaf. Four males were seen for a time in about a 3 ft. square of space. (The next day) On arrival 5 T. illotus were noticed in the same iocation. Tile-five ••• diminished to one about noon . They varied their position within this space but always returned to it following a quick dash after some indeterminate object. On returning, two or three would be closely following each other and would often alight on the first one to COTtle to rest as if seeking copulation. They wou1d immediately assume a still pose on their perch, the body slightly elevated 9

anteriorly, the abdomen usually touching the leaf behind, with the genitalia slightly protruding. In this pose, the front legs were usually doubled up underneath and not grasping the perch, but raised as if in a tactile or sensory position of some sort. Immediately after alighting, they took a firm hold with the four posterior legs and rubbed the anterior legs together but never stroked the head as house flies do. At the approach of some interesting specimen, they ceased stroking the tarsi togther and lowered legs. elevating the knees in short jerks, acting as if trying to sense something before taking off after it. The object of their sorties could not be ascertained, the short dashes, when followed, seemed to be out and back for an unseen or for no particular object. Two or three times a female tabanid whirled around me and attracted a frenzy of attention on the part of the males flying up and away after the departing female but thier chase could only be followed with the eye momentarily. Once in a while an unidentified female would attract no notice, perhaps being of another species. One wonders if a tuning fork of the right pitch would cause simultaneous reactions. It was occasionally noticed that a male would drop his front legs and start crawling, at which time no notice was taken by it when the others darted off in pursuit of something (Philip. 1931). Other published material concerning sound produced by Tabanidae deals primarily with the fact that hovering males produce a distinctive whine (Evans, 1966; Nash and Ross, 1977; Mosier and Snyder, 1918), and that female Goniops chrysocoma produce a characteristic buzz during ovi position and maternal behavior. In this case the "buzz" sound is produced "with the wings lifted up and forward, from which position they are rapidly vibrated, but not to such an extent as to touch the leaf" on which she has positioned herself to guard the egg mass (McAtee, 1911; Schwardt. 1934). 10

Finally, field experience with horse and deer flies leads to more speculation. "Anyone having occasion to go near the woods is quickly aware (of Tabanidae) by the peculiar hum or rustle of their wings as they circle about the head. The insistent hum of the larger tabanids is readily distinguished, but the approach of a deerfly is frequently missed before it alights or begins feeding" (Philip, 1931). Collectors of tabanidae such as myself and Dr. l. l. Pechuman (personal communication) agree that one can often recognize species by the sounds produced by attacking females. This ability of collectors is indirect evidence that various species of Tabanidae produce unique sounds. METHODS AND MATERIALS

Collection Techniques Tabanid specimens were obtained by rearing adults from field collected late-instar larvae and by field collecting adults. larvae of Chrysops cincticornis. f. niger. f. callidus. and Tabanus reinwardtii were collected in May 1978 at Rockmill Dam Reservoir in Fairfield Co .• Ohio. Specimens were reared in paper cups partially filled with the substrate in which they were collected. These cups were covered with perforated plastic cups with slightly larger rim diameters (Fig. 1). Rearing cups were stored at room temperature and were regularly watered. maintaining substrate moisture . Carnivorous Tabanus larvae were placed individually in rearing cups. and Chrysops were reared in groups of up to five per cup. Adult Tabanidae were collected using either a modified Malaise Trap baited with dry ice and a shiny black sphere (Fig. 2) or an aerial net. The lack of collecting heads on the trap was essential for obtaining specimens in good condition (Drees et al .• in press). During 1978. collections were made throughout Ohio and in West Virginia in order to obtain unusual or locally restricted species. However. in 1979. collections were made on a weekly basis at Cedar Bog Nature Preserve. Champaign Co .• Ohio. after obtaining a collecting

11 12

permit from the Ohio Historical Society. Complete collection data for specimens recorded are presented in Appendix A. Specimen identifica tions were confirmed by Or. L. L. Pechuman, Cornell University. Specimens collected in the field were placed in plastic poultry bags and then stored in an ice chest at approximately 15°C. The low temperatures and lack of light in the cooler effectively immobilized specimens until recordings could be made. Recordings of wing stroke sounds were made in the evening hours (8:00 p.m. to 1:00 a.m.) on the day of capture. This recording schedule standardized the behavioral conditions of the flies and also permitted specimens escaping from the holding chamber to be readily retrieved at the room light. Reared specimens were recorded as soon as possible after emergence, however, the exact time of eclosion could not be determined.

Recording Techniques A portable recording chamber was designed and constructed to exclude extraneous noise and to insure consistency of the acoustical environment (Fig . 3). The exterior surface was painted with white enamel to help maintain the inside temperatur~ as cool as possible during field recordings. The chamber was constructed around a Freeze Safe Polyfoam Packers Co. insulated container. This structure was first wrapped in aluminum foil and then encased in a 3/4 in. (1905 mm) thick plywood box with a hole cut in one side to house the microphone installation. Four rubber stoppers were fastened to the outside of the bottom to dampen 13 sounds from the ground. An inner chamber was constructed of similar plywood, also with a hole for the microphone. and the space between the inner chamber and the inner surface of the cooler was filled with matted fiberglass ceiling tile. The inside surface of the inner chamber was also covered with ceiling tile. The top of the chamber was similarly constructed, although a rectangular hole was cut into it to house the felt covered specimen holder mount (Figs. 3 and 4). When the top of the recording chamber was attached to the outer plywood box with screws, the specimen holder mount fit snugly into the inner chamber, and the felt layer formed a sound barrier between the inner and outer plywood chambers. The mount enabled a specimen holder to slide easily in and out of the recording chamber. The specimen holder was constructed from 1/4 in. (6.35 mm) plexiglass and 1/8 in. (3.175 mm) diam. plexiglass rods (Fig. 4). A thermometer inserted in the specimen holder was secured with rubber stoppers . Four dead air spaces near the top of the holder formed a sound barrier while still permitting light to enter the chamber, facilitating the flight response of specimens being recorded. Specimens were attached to the tethering rod, and the height of this rod was adjusted so that the flies could rest on a plexiglass platform or trap door. By pressing on the rubber stopper attached to the top of one of the platform support rods, the trap door would lower away from the fly causing it to behave as if it were in flight. Releasing the rubber stopper resulted in the return of the platform to its original position because of a spring mechanism on the platform 14 support rod. As the specimen again made tarsal contact with the platform. flight activity terminated. The microphone installation was constructed from cardboard tubing covered with felt. A UHER M517 microphone was suspended in this tube, supported by rubber stoppers with holes drilled in them into which the microphone was inserted. The space remaining in the tube was filled with foam rubber to dampen sound. The microphone installation could be removed from the recording chamber for oral editing and commentary. and then be reinserted to the proper depth for specimen recordings. The distance from the microphone to the specimen was one inch. Recordings were all made on Scotch 176-1200 URS magnetic tape using a UHER 4000 Report 5 portable tape recorder at a recording speed of 7-1/2 inches per second (ips) or 19 em. per sec. (cps). The UHER 4000 has an audio range of 40-20,000 cps or Hz. a signal to noise ratio at 7-1/2 ips greater than or equal to 52 dB, and wow and flutter of! 0.15%. Accurate tape speed was also verified by timing a reel of tape of known footage. The recording level was consistent for all but the larger tabanid species. including Tabanus sulcifrons, l· calens. l· nigrescens, and l· atratus. Recording times per specimen were generally between 15 and 30 seconds, although specimens displaying variations in sounds were recorded for longer periods and uncooperative specimen recordings were generally shorter in duration. The temperature. time of day , and date were recorded for each specimen taped. 15

Wing Modifications or Mutilations Wings of 17 specimens were altered after initial recordings of normal wing stroke sounds were made. Modifications were performed using dissecting scissors in one of the following manners: 1) Both wings were truncated {cut perpendicular to the long axis of the wings). 2) Both wings were tapered or cut at a slight angle to the long axis of the wing, narrowing the wing shape and reducing the chord. 3) One wing was cut in one of the manners described above. This method seldom resulted in both wings being of equal size or shape. After recording the sounds of the modified wings, the specimens were treated as described below, and the original wing lengths and areas were estimated by comparing the remaining wing size and shape to those of normal specimens. The area of the removed wings was calculated by substracting the area of the remaining wing from the estimated area of modified wings.

Temperature Modifications Although the recording temperature of each specimen was noted, the effect of temperature changes on individuals was also examined. Eight specimens were recorded at ambient temperature and removed from the chamber. A hair dryer was then used to heat the chamber, and the specimen holder was reinserted. After the temperature stabilized, the flies were recorded again. This process could be repeated, noting the new temperature before each recording. 16

Unfortunately, this experiment could not be replicated because of the inability to cool the heated chamber.

Sonagrams Tape recordings of Tabanidae were edited and deposited in the Borror Laboratory of Bioacoustics in the Department of Biological Sciences, The Ohio State University. Specimen recordings were replayed on a Technics 1500 (Panasonic) tape recorder through a Scott 44A integrated amplifier into a Kay model 7029A Sona-Graph. Each specimen recording of acceptable quality was graphed on Kay Elementrics Cooperation type B/65 sonagraph paper, with the following settings: frequency range 10-1000 Hz, gain equal, calibration at every 50 cycles, narrow band, mark level and AGC on 4, and with a linear scale. All of the variations of sounds produced by a specimen were depicted, while only four or five seconds of steadily "flying" specimens were graphed. The entire recording and graphing technique was calibrated using a tuning fork of the musical note "A" at 440 cycles per second (cps) (Fig . 8). Each sonagram was also marked with a frequency calibration mechanism wh i ch produces horizontal marks on the graph at every 50 cps. These calibration marks were used to produce a ruler with 10 cps increments (Fig. 10). This device was utilized to measure the frequency bands of the sounds present in the specimen recordings . Both the maximum and minimum wing beat rates in each sonagram were measured in order to determine the frequency ranges for each species. For species comparisons, however, only the maximum wing beat 17

rates were utilized. The fundamental tone or wing beat rate was calculated for each specimen by averaging the differences between all of the frequency bands (fundamental +harmonic overtones). This method was used to overcome possible inaccuracies in the measuring device.

Loudness The loudness of each specimen recording was estimated by direct readings from a VU meter on the Technics 1500 tape recorder with a constant output setting. The VU meter measures the loudness of the recording in units relative to intensity in decibels. The output level was 8 for Tabaninae and 10 for the smaller and softer Chrysops. These readings were made while playing the specimen recordings at 15 ips.

Anatomical Measurements Wet Weight: Directly after the specimens were recorded. they were freeze killed in the plastic poultry bags. Each fly was then weighed on a Mettler Type H16 Balance to the nearest 10-4 g in order to determine the wet weight or body mass. Flies were weighed individually to prevent thawing, and then they were placed quickly in 2 dram (17 x 60 mm) Kimble Shell Vials and sealed in with Parafilm "M" Laboratory Film. Vials were stored at -18°C in a Sears Coldspot Frostless refrigerator-freezer. Some specimens were pinned and mounted rather than being frozen. 18

(5.56 mm) wide Scotch splicing tape. In this manner, ~any wings of one species could be mounted together on a single slide. Wing slides were then projected with a Bausch and Lomb VH Micro-Projector calibrated with a B&L micrometer so that 0.1 mm of the mounted wings equaled l/16 in. (1.5875 mm) on the wing drawings (a magnification of 15.9 times). All wing measurements were made from the resulting wing drawings.

Wing Length: The distance from the apex of the wing to the distal base of the tegulum was considered to be the wing length, and the line between these points has been designated as the wing span line (Fig . 5).

Chord: The width of the wing, or chord, will vary along the length of the wing. The chord line, drawn perpendicular to the wing span line, will be longest at a point along the wing span line referred to as chordmax· The point at which chordmax occurs is measured at a set distance along the wing span line. In this study, chord lengths were measured at approximately 25 and 55% of the span line as measured from the base of the wing. 19

Wing Area: The area of each wing was calculated by weight. All of the wing drawings were Xerox-reduced to 62.5% of their original size. Each wing was then cut out to be weighed. To simplify the cutting procedure and to insure consistency, the wing bases were truncated by cutting along a line extending from the humeral cross-vein to the basal-most point of the axillary cell. The weight of each wing was then divided by 1/4 of the weight of a 25/32 x 25/32 in. (19.84 x 19.84 mm or 2 cm2) piece of Xerox paper, or rather the weight of 1 mm 2 of wing surface.

Wing Loading: The body mass (wet weight) of an insect divided by the total surface of both wings is known as the wing load, and this value is used to determine how much power is needed by that insect to fly. Values for wing loading were calculated for each specimen recorded for which data were available.

Effective Aerodynamic Center: The lift required by Tabanidae in order to fly is generated primarily by flapping. Lift produced by forward speed or gliding is negligible (Appendix B). The effective aerodynamic center, EAC. is calculated by first determining the effective aerodynamic center of the span, (EAC)s• and then the effective aerodynamic center of the chord, (EAC)c. Combined, (EAC)s and (EAC)c define a point on the wing at which the mean aerodynamic forces acting on that flapping wing occurs. 20

The effective aerodynamic center of the span takes into account that the wing tip velocity is higher than that of the wing base, that the chord length changes along the wing-span line, and it assumes that the angleofattack along the wing span line is constant. As a result, the effective aerodynamic center. EAC, is dependent upon the shape of the wing: a wing with a narrow tip and a wide base will have a more basal EAC than a wing with a rounder tip and a narrower base. The effective aerodynamic center of the span (EAC)s• is calculated by first dividing the wing into a number of equal segments along the wing span line, which has a length, L, representing the total wing length (Fig. 5). The number of segments is n. and i is the segment number as counted from the wing base. In the middle of each segment. the chord length, Ci' is measured. Now the width of each segment is L/n, and the area of each segment is L/n·Ci. The aerodynamic force on each segment is equivalent to: L·l/n·C.·W 2·(i-l/2)2 1 max where Wmax is the flapping velocity of the wing tip. The aerodynamic moment at the base of the flapping wing is: L·l/n·C.·W 2.(i-l/2)3 1 max and, the total aerodynamic moment for the wing is obtained by summing the aerodynamic moments of all of the segments: 21

The effective aerodynamic center of the span, (EAC)s, is then calculated by dividing the total aerodynamic moment by the summation of the aerodynamic forces on each segment and dividing this value by the wing length, L, as follows: n ~{(i-l/2) 3 ·Ci} 1 (EAC) s ) =! L · ~ n----- ~{(i-l/2) 2 ·C;} 1 The product, multiplied by 100, is the percent of the wing length from the base of the wing at which (EAC)s occurs. The effective aerodynamic center of the chord, (EAC)c' is calculated in a similar manner when it is assumed that the local aerodynamic center of each segment is at 1/4 chord length from the leading edge or costal margin. This is in accordance with classical aerodynamics. The difference between the segmental EAC (the inter section of Ci and the wing span line) to costal margin distance, a1 (Fig. 5), and l/4 c1 is calculated for each segment. Then the aerodynamic moment is calculated about the wing-span line and divided by the summation of the aerodynamic forces on each segment, and the result is divided by the wing length, L: n ~{(i-l/2) 2 ·c ·(ai-l/4Ci)l 1 1 (EAC)c "'f · ..:..------ ~{{i-l/2)2·C.} i 1 22

The product of this equation, multiplied by 100, is a percent of the wing length which represents the distance in front of (if (EAC)c is positive) or behind (if (EAC)c is negative) the wing-span line where the effective aerodynamic center of the chord lies. For a sample calculation the effective aerodynamic center, see Appendix C. RESULTS AND DISCUSSION

Elements of Tabanid Flight Sound Tethered flies, upon losing tarsal contact with the trap door, began actively flapping their wings. Their legs folded and were held in an attitude to the body (Figs. 6 & 7) typical of normal flight (Nachtigall, 1968). For this reason and for the sake of brevity, the sounds of the flapping wings produced by the tethered flies will subsequently be referred to as flight sounds. Tabanid flight sounds are produced by the flapping of the wings through the wing stroke cycle. The ccmplex movements of the wings through this cycle have been described for Calliphora by Nachtigall (1968) and were not examined further for Tabanidae. However, the assumption is made that the wing stroke cycle in Tabanidae is similar to that of other Diptera. As a result of the thoracic click mechanism (Pringle, 1957), both wings beat synchronously at all times. The halteres, the only other actively moving structure on the thorax, "vibrate with the same frequency as the fore wings but in antiphase" (Chapman, 1971). Due to their small size, their movement produces no significant noise. The net result of the wing rr.ovements is the displacement of air to produce the thrust and lift required for flight. As a by-product, sound is produced with a frequency equal to the rate at which the

23 24 wings beat. Hence, the wing beat rate is often referred to as the wing-beat frequency. The frequency of the wing-beat rate is also called the fundamental tone. A total of 420 tabanid specimens, representing 39 species in 6 genera, was recorded, sonagraphed, and measured. Figures 11 and 12 depict the mean maximum wing stroke rates and standard deviations measured in cycles per second (cps) for the 39 pangoniine and tabanine species recorded. Species are listed for each subfamily in the order of decreasing wing beat rates recorded for all temperature levels and throughout the two collecting seasons. The range limits for specimens recorded were 91 cps for a female Tabanus atratus to 193 cps for a male I· guinquevittatus. Unlike the type of sound wave produced by a tuning fork (Fig. 8), the sounds produced from dipteran flight are produced in pulses. These pulses result from the thoracic click mechanism in which the upstroke is much faster and louder than the down stroke (Bennet-Clark and Ewing, 1968). As a result of the pulse type wave, harmonic overtones are produced with frequency levels at multiples of the fundamental tone (Fig. 9) (Webb et al., 1975). The intensity of these overtones decrease and decay as their frequency levels increase. The number of harmonics seen in any particular sonagraph results from the loudness of the actual wing stroke noise, the distance of the specimen to the microphone and the input and output level settings of the recording and playback equipment . Nevertheless, the intervals between the harmonic overtones are predictable from the fundamental tone (Fig . 9). 25 Other non-harmonic overtones occasionally appear in sonagrams.

These include frequency levels at ~ the distance between harmonic intervals (Fig. 13) and occasionally at 1/3 the distance. Although not artifacts, these overtones do not occur consistently within any species. No explanation for their occurrence has been attempted. Possible sources for artifact sounds with the recording technique employed were 1) wings hitting the tethering rod, 2) torn wings, and 3) resonance of the tethering or platform support rods produced by the specimen being recorded. The latter case occurred occasionally with larger specimens, but the problem was corrected by dampening these rods. These problems were usually audible at the time of recording and were corrected or the recordings were discarded.

Temperature and Sound The influence of temperature on the rate of movement and sound production for cold-blooded animals such as insects has been well documented in the literature. Although Greenewalt (1962) did not consider this factor. Costello (1974) has discussed the effect of temperature on the wing-beat frequency of mosquitoes. During this study, specimens were recorded at ambient temperatures ranging from 22 to 33°C. This range was divided into 3 groups, 101 specimens were recorded at a temperature less than 26°C, 229 specimens between 26 and 28°C, and 89 specimens above 28°C. Of the 30 species recorded at more than one temperature range. only 14 had higher average frequencies at higher temperatures (a positive response). 26

In other words, fewer than ~ of the species had faster mean wing beat rates at higher temperatures. Furthermore, the degree of positive or negative response among species was inconsistent. These results indicate that the extent of variation of sound produced among individuals is too great and overcomes the more subtle changes in frequency induced by temperature changes. A more direct approach is to study the effects of temperature on individuals. Each of the seven tabanid specimens recorded at two or more progressively higher temperatures (range 22 to 35°C) displayed a positive linear response (Fig. 14. line 3). The average positive response was an increase of 3.4 cps per degree (SO= 1.6). This figure is less than the 6.3 to 6.7 cps/1°C reported for Aedes aegypti females by Costello (1974). One specimen, a female Chrysops beameri recorded at 26, 27, 30, and 33°C (Fig. 14) displayed positive responses between the 26 and 27°C, and between the 30 and 33°C recordings. However, between the 27 and 30°C recordings the specimen decreased its wing beat rate 16 cps (from 148 to 132Hz). Although such a decrease may not have been as pronounced if the specimen had actually been in continuous flight, the observation has significance because it illustrates clearly the behavioral component of wing-beat-rate control. Costello (1974) argues that temperature induced changes in wing beat rates are associated with physical processes of the muscle tissues, the exoskeleton and resilin components rather than thermochemical reactions of the indirect flight muscles. However, as Pringle (1957), 27 mentions, "the extent of the departure frcm harmonic motion (the amount of click action) is fully under the control of certain accessory indirect muscles-- the pleurosternals of Diptera". Although behavioral control of flight speed may not be as noticeable in mosquitoes, different sounds produced by individual Tabanidae are often noticeable even under field conditions. Moreover, it is this capacity for behaviorally modifying the wing beat rate that results in the amount of variation of wing beat frequencies recorded among the individuals of tabanid species, obscuring the effects of temperature on a group of specimens. The decreased effect of temperature changes on the tabanid vs. culicid wing-beat rates could lead one to speculate that ambient temperature changes have less effect on insects with greater body or muscle masses. Although Hocking (1953) reported the inability to initiate flight in Tabanus affinus below 50°F (10°C) myogenic heat is produced once flight activity begins. Many authors (Gaul, 1951) have found the temperature of the wing muscles during flight may be much higher than the ambient temperature. Some flying insects have thus been claimed to be heterothermic, or animals which "can produce enough heat to sustain an elevated body temperature but that become essentially ectothermic ~1hen they are inactive or dormant" (Heinrich and Bartholomew, 1972). The absence of significant differences among individuals of different species recorded at various ambient temperatures tends to support this assumption. Small animals have comparatively more surface area to volume than larger-bodied species 28

and therefore lose heat more rapidly to their environment. However, no quantitative relationship can be established from the data available because 1) the amount of tracheation to surface area of a mosquito or tabanid thoraces is not known, and 2) Heinrich and Bartholomew (1972) found that the thoracic temperature of a tethered insect is less than that of an insect in free flight. For the sake of consistency and to ensure that the effect of temperature was negligible, however, only those specimens recorded in the temperature range of 26 to 28°C were utilized to compare differences among species. Specific means recorded in this range tended to cluster more tightly due to the high number of samples and possibly the effect of a small temperature range (Fig. 15).

The Effect of Wing Dimensions, Wet Weight and Wing Loading on Flight Sound The effects of physical dimensions on sound production were investigated during this study. Possible physiological influences of age and energy available for flight were not considered, but will be discussed in a later section along with the possible effects of behavioral factors. Environmental factors including temperature and time of day have been controlled. Table 2 lists the results of the physical parameters measured: wing length. wing area, wet weight, and wing loading. The wing-beat frequencies of specimens recorded at 26 and 28°C have also been provided. TABLE 2. Means, standard deviations, and sample sizes for wing lengths, wing areas, wet weights, wing loads and wing-beat frequencies (26-j,~°C) for thirty-nine species of Tabanidae. WII«l LEI'CIH (mn) Wll«l AREA (IIIII ) WliT WEHHJ' (mg) IIJI«l I.OADIOO (mg/nm2) wml-BI!AT ~ (cps) 26·280C Pangonlinao: 10.13t 0.25 (3) 23.8h 1;03 (2) 39.10t 3.30 (3) 0.80• 0.11 (2) 7.1h 0.37(14) 13.37t 1.27(12) 9.30t 2.30(12) 0.32• 0.06(10) 143. 32t: S. 90 (S)

3. Chrysope brunneus 8.13t 0.61 (3) 15.9St 2.62 (3)

4. Chrysop• cdJtdue 7.65• 0.35(17) 14.41• 1.94(14) 19.40t 5.00 (5) 0,59t 0.10 (3) 157.46• 7.30(13)

5. Chryaope c1nct1corn1• 7.67t 0.61(12) 14.30t 2.47(13) 139.09tl2. 70 (6)

6. Chrysops cuclu• 8.00• 0.42 (2) 14.73t 1.42 (2) 137 .13• 5. 83 (2)

7. Chrysops fJ•••idus 8.25t 0.21 (2) 17.93t 1.23 (2) 12.30 (1) 0.36 (1)

8. Chr!lsope gem1n4tus 6.04i 0.49(16) 9. 72t 1.35(13) 6. 75• 3.40(13) 0.33t 0.07 (7) 153.27• 9.43(11) 6.68t 0.21 (5) 11.31t 0.69 (4) 8. 70 .. 2.40 (4) 0.36. 0.09 (3) 148.65• 0.21 (2)

10. Chrl}aops 1 ndus 8.27• 0.23 (3) 17.60t 0.90 (3) 16.80 (1) 0.541 (1) 135.00 (1)

11. Chr!lsope ...cquartl 7.10t 0.31(19) 13.38t 1.47(17) 8.20• 1.80 (8) 0.30• 0.08 (6) 136. 85*12.04(13)

12. Chrysops ..,.chua 8.0 (1) 17.99 (1) ---··········--

13. Chrysops nlger 6.93t 0.25 (3) 12.07• 1.10 (3) 9.5 (1) 0.39 (1) 142.50• 3.54 (2)

14 o Chr!ISOpe p1ke1 7.04• 0.32 (8) 12.48• 1.27 (7) 9.10• o. 70 (5) 0.37• 0.62 (4) 141.20• 7.95 (S)

15. Chrl}sops sherllWU11 8.20 (1) 16.57 (1) ------132.00 (1)

6.53• 0.39(19) 10.40• 1.37(19) 10.42• 3.50 (9) 0.44• 0.12 (8) 145.50• 5.90 (6)

17. Chrysops vltt•tus 7.87• 0.44(28) 15.56t 1.84(25) 11.25t 3.45(11) 0.39• 0.10 (6) 129. 69t10. 81(23)

Tabanlnae

18. H•ema topot4 r•r• 7.40+ 0.23 (S) 13.16+ 1.13 (5) 9.80+ 0.70 (1.) 0.36+ 0.06 (3) 2 2 ~ WING LENG!tf!nm} WING AREA ~nm } WET tJEIGIT {mg} WING UlADING {111R1m 1 WING--BEAT FR00UENCY {9!s} 26-28°C 19. At!llotus b.lcolor 8.50• 0.56 (5) 17.09t. 2,61 (5) 2S,70t 7,50 (4) o. 79t 0.21 (4) 174. 72t. 9. 73 (5) 20. At!llotus oh1oeM1s 7.10• 0.43 (8) 12.01-t 1.50 (8) 13.95t 9.26 (8) 0.43t 0.09 (8) 158.67t 9.62 (6) 21. H!11>om1tra d1fr1c1lJ.s 12. 37t 0.40 (3) 32.46t 0.55 (2) ...... 119.50t 9.69 (4) 22. H51bolll1 tra pachuJIIotn1 9.50 (1) 20.16 (1) 45.30 (1) 1.12 (1) 149.17 fl) 23. Hybom1tra laslophthalN 11.01* 0.59(14) 26.17t. 2. 78(10) 42.90t 9.93 (6) o. 78• 0.13 (4) 137.92• 8.25 (2) 24. H!1bom1tra 1111crocephala 11.90• 0.66 (3) 32.02t. 4.97 (3) .. .. ------...... 119.43t 2.23 (2) 25. Hybom1 tra .Unuscula 8. nt. n. 53(26) 17.26t. 2.28(25) 21.96t 6.94(17) 0.68t 0,09(16) 135.19t17. 33(20) 26. Hybom1 tra aodaH• 11.60• 0.61 (4) 31.22• 2. 76 (4) 76.50t15. 79 (5) 1.08:t. 0,04 l3) 137 .04dl. 30 (3) 27. T•banus a:tr•tus 23.10 (1) 123.4 (1) 397.0 (1) 1.59 (1) ...... 28. ranabus calen.s 20. 7St. 1.63 (2) 95.93•17.56 (2) ...... 102.80 (1) 29. 2'abanu• nJ grescentl 19.13t 0.12 (3) 82. 73t 6. 75 (3) 329.2.t13,50 (3) 2.00• 0.19 (3) 115.00d4.43 (3) 30. Tabanu• n1gr1pu 9.65• 0.43(28) 21.63t 2.32(24) 39.80.tl0. 78(26) 0.91* 2.32(24) 139. 35t23. 36(20) 31. Tabanu. ,pum11us 7.28t 0.35(16) 12.88t 1.28(15) 19.60t 8.16(13) 0. 77t. 0. 26(13) 154.15tl0.16 (8) 32. Tabanus qu1nquev1ttatus 9.29t. 0.42(23) 21.86t 2.05(19) 41.66t 6.99(17) 0.96t. 0.07(15) 148. 73t16.28(16) 33. Tabanu. re1nwardt11 13.53• 1.07 (3) 43.81t. 7.32 (3) 117.0 (1) 1.13t (1) 125.00 (1) 34. Tabanus sacken1 12.12• 0.53 (6) 33.65• 2. 77 (5) 67 .28t 0.02 (6) 0.92.t 0.10 (5) 123.40t.10.47 (2) 35. Tabanu. s1111111s 10.34• 0.45 (7) 25.22t 1.90 (7) 44, 70U1,58 (7) 0.82• 0.10 (7) 137.2St.l6.80 (5) 36. Tabo~nus s,parus 111ller1 7 .SSt 0.32 17) 13. 99t 1. 38(17) 21.06t 7.50(16) o. 79• 0.14(16) 163.60t 9.93(12) 37. Tabanus sulci froM 17.50• 1.15(14) 72,57t. 4.12 (9) 217.96t.25. 72(12) 1.56• 0.09 (7) 121.62t. 7 .21(10) 38. Tabanus su,perj~UJ~~tntar1us14.19t 0.58(17) 47.1&t 4.03(16) 122.18:ll8.00(11) 1.32• 0.12(10) l18.96t 6.45 (8) 39. Tabanus tr1macu1ata 13.19t 0 . 71(15) 40.22t 4.88(11) 123.00•29.60(10) 1.52t 0.41 (8) 127 .61t.l3.09 (8) 40. Tabanus v1var 10.10 (1) 23.54 (1) 38.60 (1) 0.82 (1) ...... w 0 31

Wing Length: Wing length (a wing dimension) and wet weight were both found to be correlated with wing·beat frequency. A high negative correlation, significant to an alpha level of 0.01, was found for the effect of wing length (X) on the wing·beat frequency (Y) for both Chrysops and Tabaninae. The regression line for 103 specimens of Tabaninae (Fig. 16) was found to have a slope of ·0.32, and data points cluster around a line described by the following equation:

v = 288.712 x-0•316 The line fitted to the data from 40 Chrysops specimens (Fig. 16) has a slightly steeper negative slope of -0.46, described by the following equation: v = 344.782 x-0·464 Plotted on a log·log scale, these lines arestraightwith ranges of 4.8 to 8.9 mm for Chrysops, and 6.3 to 23.1 mm for Tabaninae. Numbered points in Figure 16 refer to the mean values of species listed in Table 2. These results were plotted along with the regression line for 13 species of Canadian mosquitoes recorded at 23°C (Belton and Costello, 1979) and Greenewalt's boundary line (Greenewalt, 1962) in Figure 17. Greenewalt's boundary line ·is apparently the upper statistical limit of wing·beat rate and wing length calculated from all insects for which this type of data occurs in the literature. Interestingly, the largest tabanids approach but do not exceed this limit. 32

Chord: Another parameter of the wing, the average maximum chord per species, occurs at approximately 25% or 55% of the wing length from the tegulum. A linear relationship was found between wing length and maximum chord such that for every 1 mm increase in the length of the wing, the chordmax will increase by 0.34 mm (correlation coefficient = 0.99). Thus, chord length is related to wing·beat frequency in the same manner as is wing length. During the measurement of these chord lengths, some tabanid species were noticed to have the average maximum chord at 55%, while other species' average maximum chord occurred at 25%. This either·or situation occurred because of the indentation along the posterior margin of the wing at the point where the cu2 + 2A wing vein (Comstock·Needham system) and the posterior wing margin join. Generally, the larger tabanid species were found to possess more tapered wings with the chordmax at 25%. These results have indicated the existence of consistent and distinct differences in the wing shapes among tabanid species -- even among species with similar average wing lengths.

Wing Area: In order to find a wing parameter which might have a higher correlation to wing·beat frequency, the wing area of each ~pecimen recorded (for which wings were available) was calculated. Values for wing area encompass both the values of wing length and chord, and thus are related to wing shape. Again, the correlation coefficients were significant to the alpha level of 0.01. However, neither the 33

coefficient for Pangoniinae (r • a -0.372) nor correlation 0 70 than those for wing Tabaninae (rn = 118 = -0.666) was more significant length and wing-beat frequency (rn. 40 • -0.551 and rn = 103 • -0.701, respectively). The relationship between wing-beat frequencies (Y) and wing area (X) for the two subfamilies was described by the following equations: Pangoniinae: Y = 217.303 x-0.16288 Tabaninae: Y = 246 .0178g x-0.17931 The difference between the slopes of these two equations (-0.16288 and -0.17931) is very small. A non-dimensional shape factor was calculated for tabanid wings by dividing the square root of the area of a single wing by the wing length (/mm 2/mm). For the 335 individuals measured. a regression line, significant to a = 0.01 {r = -0.46585), for the relationship of wing length {X) to this shape factor {Y) is described by the following equation: v • 0.56131 x-0·6168 The mean shape factors for 40 species measured have been plotted together with mean wing lengths and appear in Figure 18 along with the regression line calculated for individual specimens.

Effective Aerodynamic Center: In order to investigate possible aerodynamic differences of tabanid wings which could result from different shapes. the effective aerodynamic center was calculated for a few of the wings which represented extremes in wing-shape variation. The effective aerodynamic centers {EAC) of the span and chord of the 34 wings of the following species were calculated:

Species {EAC)s {EAC)c

Chrysops bruneus ~ 70.8% 2.8%

Chrysops bruneus ~ 70.7% 2.2%

Chrysops bruneus ~ 71.1%

Chrysops cincticornis ~ 68.9%

Chrysops cincticornis ~ 69.1%

Chrysops geminatus ~ 70.9%

Chrysops moechus ~ 69.3%

Haematopota ~ ~ 70.5%

Haematopota ~ ~ 70.3%

Hybomitra difficilis ~ 69.3%

Tabanus nigrescens ~ 69.0% 0.9%

Tabanus .!!.!9.ri pes ~ 70.1%

Tabanus guinguevittatus ~ 70.5% Y = 70.0%

Results indicate small. but consistent differences among species. As predicted, the more tapered the wing, the more basal the (EAC)s and the closer the (EAC)c to the wing·span line. However, the minor differences in the EAC of these species indicate that the methods by which Tabanidae achieve flight aerodynamically are very similar, and that wing shapes will at best have minor or secondary influence on wing·beat frequency. 35

Wet Weight: The wet weight of specimens was measured for 241 of the specimens recorded. Because of the collecting methods employed, the assumption was made that all specimens were unfed or partially fed and were in pursuit of a bloodmeal (Duke et al., 1956). Even with this assumption, the average standard deviation from the mean wet weight (90.7%) was about 1.5 times greater than the standard deviation from the mean wing length (59.9%). In other words, wing length is a more consistent parameter. This variation in wet weight can be due to the fact that Tabanidae, besides feeding on blood needed for ovariole development, will imbibe fluids such as nectar in order to maintain energy required for flight. Nevertheless. the correlation between wet weight and wing-beat frequency was still significant to the alpha level of 0.01. at least for Tabaninae (rn = 103 = -0.650), but less significant than the correlation between wing length (Y) and wing-beat frequency (X). The equation for the regression line is Y = 199.439 x-0·9499 • The correlation for Chrysops was not significant. Measurements of weight and wing length by Hocking (1953) of unfed females of Tabanus affinus, I· septentrionalis, Chrysops furcatus and f. nigripes agree closely to those for similar sized tabanids in this study. Greenewalt (1962) has determined regression lines for the relationship of wing length (X) and wet weight (Y). His figures show two regression lines. one for birds and one for insects: 36

Birds: X = 0.0079 v2•899 or Y = 5.3101 x0·3449 2 9617 0 3376 Insects: X E 0.677 v · or Y = 2.4817 x · Regression lines for Pangoniinae and Tabanidae recorded during this study are shown in Figure 19. The equations for these lines are as follows: 4 1105 0 2433 Pangoniinae: X~ 0.00317 v · or Y E 4.0538 x · Tabaninae: X = 0.00419 v2· 9863 or Y = 2.8433 x0·3350 (NotethatGreenewalt has given the equation for the relationship between body weight vs wing length, but his slopes indicate the relationship between wing length vs. body weight. Thus, Greenewalt's equations are given first, followed by equations describing lines A, B, C, and Din Figure 19.) Except for Pangoniinae, all of these lines have a slope of 3. Interestingly, all of the data points for Tabanidae measured during this study fall above Greenewalt's line for insects, as do Hocking's (1953) data points for unfed female Tabanidae. However, after feeding on a sugar solution. the weight of Hocking's Tabanidae fell slightly below Greenewalt's regression line. The effect of a blood meal on body weight is even more dramatic . Gooding {1972) has summarized methods for measuring bloodmeal sizes for hematophagous insects, and has compiled estimates for Hybomitra frontalis {Walker) {=I· septentrionalis) and~· affinis (Kirby) by Miller {1951), and for Tabanus guinguevittatus Wiedemann and I· sulcifrons Macquart by Tashiro and Schwardt {1949). Values indicate an average increase of about 217% the weight of unfed females after feeding to repletion on blood. This increased weight would shift the 37

regression line in Figure 19 calculated for unfed Tabaninae to the right, to the other side of Greenewalt's regression line for insects (D). Added body weight could affect the wing-beat rate if the angle of attack of the wings during the wing stroke cycle does not change.

Wing Loading: One method of discussing the effect of body weight aerodynamically, is to express the relationship between wing area and wet weight in terms of wing loading: body mass/area of both wings. As values of wing loading increase, either the weight of the body is increasing relative to the wing area, or the wing area is decreasing relative to the body weight. Among tabanid species, there is tendency for wing load values (Y) to increase with increasing size or wing length (X) (rn = 204 = 0.79121) such that: Y = 0.0345 X1.3733 Theoretically, as wing loading increases, the power needed for flight should also increase. Increased power can be achieved by Diptera in two ways: 1) by increasing the wing-beat rate and 2) by increasing the angle of attack during the wing-stroke cycle. Although wing loading increases with size, there is a negative correlation between wing loading (X) and wing-beat frequency (Y), at

least for the mean values measured for tabanine species (rn = 16 -0.7349), such that the equation for the regression line is:

Y = 135.851 X-0.2108 These conflicting phenomena, plus the structural aspect of tabanid wings, play an important role in establishing the upper limits of 38 tabanid size relative to the capacity to fly. "In similar figures the surface increases as the square and the volume (V) as the cube, of the linear dimensions (L)" (Thompson, 1952). Likewise, in Tabanidae the wet weight (Y) increases proportionally to the square of the wing area (X):

v = o.o175 x2 (Greenewalt's formula for the relationship between wing area and body weight had a slope of 1.5 rather than 2.0.) As scale increases then, there will be a point at which the lift generated by wings of a certain area will be overcome by the more rapidly increasing volume or mass of the body. Of course, the mass of the female tabanid must also include the weight of the bloodmeal. The discussion above has attempted to describe the effect of scale on wing-beat frequency and wet weight among tabanid species. However, the effects of wing loading are most clearly evident when comparing species or groups of species of similar size. Three species of Chrysops and two tabanine species all have an average wing length of 7.2 mm (Chrysops beameri, f. pikei, f. callidus, Atylotus bicolor, and Tabanus pumilus). The regression lines for wing-beat rate vs. wing length indicate that Tabaninae have higher beat rates than Pangoniinae of equal size (Fig. 16). The difference between the two groups was found by comparing means for wing loading of 17 Chrysops specimens and 21 tabanine specimens using the Student-Newman-Keuls test. Results indicate a difference in wing loading between the two groups significant to the alpha level of 0.01. This difference in wing loading for unfed 39 females of the two subfamilies, resulting from the increased body mass (perhaps muscle mass) in Tabaninae, provides an adequate explanation for the observed differences in wing beat rate. Among the members of a single species, the effects of wing loading on wing-beat rate are obscured. No significant correlation \tas found for either the effect of wing length, or wing loading with the wing beat rate. Apparently, the technique of tethering specimens for recording has led the flies, free from the effects of gravity or drag, to display their full range of flight behavior in an attempt to escape. (Many specimens, of course, beat their wings or "flew" very steadily while tethered.) Sotavalta (lg47) has discussed the effects of tethering insects in a fixed position for a number of insect groups and has found that Diptera, "which possesses the greatest relative elevating power (up to 200% of the body weight excessive)" of all insects, were among the most active when tethered. His findings agree with Chadwick (1939) that "a fixed insect is an insect with a full load". Apparently, individual specimens of one species have the capacity to achieve both the maximum and minimum wing-beat rates possible with their morphological and physiological characteristics, whether or not they have just fed on a bloodmeal (energy for flight is supplemented by the intake of carbohydrates). Similarly, there is no reason to assume that unfed flies will always fly with lower wing-beat rates. Again, flies can achieve the power needed for flight by balancing the effects of the wing-beat rate and the angle of attack during the wing stroke cycle. Thus, an unfed fly can beat its wings at a high rate 40 while "feathering" or decreasing the angle of attack during the wing beat cycle to achieve a relatively low forward speed. Wings of 17 tabanid specimens (6 species) were modified by either truncation or tapering. The wing-beat rates of 95% of the specimens increased after modification. These results agree with those of Sotavalta (1947). However, no significant correlation was found between the amount of wing area removed and increased wing-beat rate, because of the small sample size. Decreased wing area changes wing loading, but the reason the wing-beat rate increases is due to the change in the resonant mechanical frequency (rmf) of the wing. According to Hocking (1953), "It seems clear that both the wing muscle system and the haltere and the muscle system in Diptera vibrate at their own resonant mechanical frequency. Were this not so, the energy loss from the repeated changes in the direction of the wing movement would surely be impossibly high. This frequency depends only on the moment of inertia of the system, and the dimensions and elastic moduli of the terga and flight muscles, but may be modified by air damping . " Though it would be a difficult task to calculate the rmf of the dipteran wing system, the implications of the existence of such a frequency are applicable to the sounds of Tabanidae: as an object increases in size, the rmf becomes lower (for example, the strings on a violin vs. the strings on a bass). Thus, larger Diptera have lower wing-beat rates than smaller Diptera. Furthermore, when flies beat their wings at a rate different than that of the rmf, more power is consumed and there exists the possibility that the elements of the sound produced by the movement of the wings will interact with the 41 elements of the wings' rmf. In fact, this is the most likely explanation for the variations in the intensities of the fundamental and harmonic overtones observed in the sonograms during this study and those described by Belton and Costello (1974). loudness or Sound Intensity The previous section discussed the implications of the resonant mechanical frequency of the wing structure, determined by the shape and size of the wing, and the elastic properties of the thoracic box. The latter results from structural composition of the thorax plus the modifying effect of the pleuro-sternal muscles as described for Tabanidae by Bonhag (1949) and as discussed for Diptera by Pringle (1957). The interaction between the rmf and the elements of the sound waves produced by the wing stroke results in interference or reinforcement of the fundamental tone and overtones of flight sounds. This capability of flying insects to increase the volume (loudness) of certain components of the sound produced may be of interest in a biological sense. Male mosquitoes have been shown to react most strongly to the fundamental frequency of the flying female (Roth, 1948). Nevertheless, the possibility that insects could detect overtones resulting from the wing beat rate cannot be ruled out. Because all but the larger tabanid species were recorded at a constant recording level, and the microphone to specimen distance was also fixed, the loudness or intensity of the flight sounds among species could be compared. loudness was estimated from a VU meter, 42 although this procedure is crude. Individual specimens are capable of modifying the loudness in two ways. 1) The intensity is directly proportional to the square of the frequency of vibration, an increase in wing-beat frequency will result in greater intensity. This phenomenon is seen in sonographs. As the fundamental tone produced by a specimen increases, the number of harmonic overtones increases. 2) Intensity is also directly proportional to the square of the amplitude of the sound wave or rather to the displacement of air. Thus, a specimen can increase its intensity by increasing the angle of attack of the wings during the wing stroke cycle, without changing the wing beat rate. This phenomenon is also evident in the sonograms of specimens recorded. Since intensity is related to air displacement, specimens with larger wing areas will obviously be louder. This phenomenon is evident from the VU readings and the average estimated intensities of the species recorded and measured, plotted against wing area.

Sexual Differences of Tabanid Sound As discussed in the introduction, only male Tabanidae are observed to hover in a stationary position. Females of certain species (i.e. Tabanus sackeni) will fly extremely slowly; however, they never actually remain stationary in the air. Hovering is the most power-demanding type of flight since no lift is derived from the forward motion. 43

Very few males were collected and recorded during this study. Of the eight males recorded (1 Chrysops cincticornis. 4 Hybomitra miniscula. 1 Atylotus bicolor. and 2 Tabanus guinguevittatus) all but two specimens had higher wing beat frequencies than the average corresponding female wing beat frequencies. Due to the small sample size. however. these differences were not statistically significant. During actual hovering behavior in nature. the wing beat rates are likely to be much more constant and higher in pitch than those recorded for males tethered to a stationary rod. Recordings of hovering behavior are highly desirable and two unsuccessful attempts were made to locate and record hovering male Hybomitra minuscula at Cranesville Swamp. Preston Co •• Hest Virginia during August of 1978 and 1979. where they had been observed to be abundant in August 1976. The lack of success during these trips was due to poor meteorological conditions --cool. cloudy weather. One may speculate, however. that if hovering is accompanied by greatly increased wing beat rates. this behavior could effectively isolate the sounds produced by males from the lower frequencies produced by non-hovering females flying past. This acoustical isolation is an essential component if the males are to detect the sounds of females. This phenomenon has been well documented for mosquitoes (Farb. 1962).

Relation of Wino-Beat Rate to Habitat Figure 16 shows the regression line calculated for the relationship of wing langths to wing-beat rates of individual tabanid specimens between 26 and 28°C. The plotted points are of species' 44 means. When examining the species which fall away or deviate greatly from the regression line, the following species stand out:

SPECIES cps AWAY FROM THE REGRESSION LINE Chrysops callidus +22 Atylotus bicolor +28 Tabanus guinguevittatus +8 Tabanus sparus milleri +12 Hybomitra minuscula -10 Hybomitra microcephala -12 Hybomitra difficilis -10 Tabanus superjumentarius -6

(The average standard deviation from the mean wing-beat rate is ~10.) A review of the habitats and distributions of these species. supplemented with personal experience, leads to an interesting generalization: Those species which are habitat-restricted to bogs or marshes, or those which occur primarily in wooded areas (this includes most of the Chrysops) have consistently lower average wing beat rates , while those occurring in more open areas, with widespread distributions (the more pestiferous species) have consistently higher than average wing-beat rates. All of these species seem to have the capacity of flying at normal rates, but perhaps they are behaviorally adapted so that their flight speed is better suited to their habits and habitats. 45

Concluding Remarks The flight sounds of 39 species of Tabanidae have been described, and the various factors which could influence the production of sound are discussed. Table 3 lists all of those factors which have been identified in the literature and in this study. Although wing-beat rate is correlated with wing length and body mass, one cannot utilize a single parameter to predict the wing-beat rate. Distinct differences occur among several of the species recorded, and their differences must be examined individually to determine whether their wing-beat rates deviate from the expected values due to physical differences, physiological factors, behavioral idiosyncracies, or all three. No inference of biological significance of tabanid flight sounds can be made from the data collected. Although some species appear to produce unique sounds, the sounds of most of the species recorded overlap to some degree. However, now that these sounds have been described, playback experiments in search of behavioral reactions such as those attempted with Asilidae by Lavigne and Holland (1969) should be attempted. The possibility exists that the c~havioral response to sound is part of a behavioral sequence. and that without the other stimuli, visual and perhaps chemical, sound alone elicits no response. Data generated to explain the physical factors influencing flight sounds serve additional functions other than the attempted inference of biological significance. Sounds generated by flapping wings describe flight, and flight in tabanids has multiple functions: 46 dispersal, seeking a bloodmeal and carrying it away, seeking other energy sources {nectar), and perhaps locating and coupling with a mate for reproductive purposes. Describing the average flight of various species yields information regarding their capacity to achieve these functions. By correlating sounds with physical parameters {wing length, wing area. body mass, wing loading, effective aerodynamic center), properties of these species have been described which are often not found in taxonomic literature, but which may be useful to workers in the area of medical and veterinary entomology attempting to determine the importance of one tabanid species relative to another. 47

TABLE 3 Factors Influencing the Sounds of Tabanidae (Diptera}

Aerodynamic Factors: Wing Morphology - Length, Width (Chord}, Area Shape, EAC Body Construction - Body Mass, Mass of Flight Muscles Wing loading - Body Mass I Wing Area Wing-Stroke Cycle - Angle of Attack

Environmental Factors: Temperature light or Time of Day Humidity

Physiological Factors: Physiological Age Energy Available for Flight

Behavioral Factors: Mating Behavior Host-Seeking Behavior Feeding Behavior Oviposition Behavior Escape and Dispersal Behavior Habitat Figure 1. Container used for rearing field-collected late instar tabanid larvae: Bottom is a paper cup filled with the substrate in which the larvae were collected. Top is a perforated plastic cup with a slightly larger rim diameter.

48 49

Figure 1 Figure 2. Two-dimensional modified Malaise trap baited with dry ice and a shiny black sphere for field collecting adult Tabanidae.

50 51

Figure 2

'\• Figure 3. Recording chamber- top view with lid removed and leaning against one side: White areas represent inner and outer boxes constructed from plywood. Cross-hatched areas are styrofoam, and stippled areas are matted-fiberglass ceiling tile. Microphone installation is inserted in a hole cut through the right side.

52 Figure 3 Figure 4. Specimen holder, constructed of 1/4 in. plexiglass and l/8-in.-diam. plexiglass rods: Specimen-holder mount, actually a part of the recording chamber is also pictured. The specimen is resting on the trap door or resting platform which can be lowered by pushing down on the stopper on the spring-loaded platform-support rod.

54 55

Figure 4

. SPECIMEN HOLDER MOUNT (mMOM&Tm AND RUBBER STOPf'ERS SPRING~~ r hr r h \ <: '.:i \ ,. t { f F '\ J \i prj t ;....;j.J u Jil %@ ~ 11 :m: I:·_:; 1: ::: 1:111.1 :::,:

I i ::::-::: U''i:': I ~ ':'l'= j : m nr.M\ E.. ~ :: p· 1m f ., I i '::\ l> i?l 1: L:.. 1-= PI lli pJ

u TETHER I NG ROll

.. ~ I --~ n j;J L p ~~

L- 1- Fig ~ re 5. The outline of a tabanid wing: T a tegulum. WSL = wing-span line. l = wing length. i =

wing segments (n • 10). Ci z chord length of

segments. ai s length from costal margin to wing-span line; dashed line represents the truncation of the wing base for calculations of the effective aerodynamic center. EAC.

56 57

Fi9ure 5 Figure 6. Chrysops cincticornis attached to the tethering rod with rubber cement, resting on the trap door: The thermometer appears in the upper left corner.

Figure 7. Chrysops cincticornis in typical attitude of flight after losing ground contact with the trap door: Legs are folded and held close to the body, antennae point directly forward.

58 59 Figure 6

J I

Figure 7 Figure 8. Sound production: The vibrating tuning fork (left) produces a displacement of air molecules into areas of rarefaction and condensation. Depicted graphically or by an oscilloscope. the displacement of moleculed translates into a a sine wave with a certain number of cycles or waves per second (cps) (lower left). The sound spectrograph or sonogram on the right is a picture of the sound of a tuning fork of the musical note "A" with a frequency of 440 cps.

60 Figure 8

SOUND PRODUCTION -·---_-...... 950 ~ -:.;."' _..

w~ - ~-- :1: eoo-.:. l; -~~- 0 - - ~ &so--=" M U)" - a: ·A· 440cpa ~ - ~ -.. 0 350- t l; > 200- w~ ::l @ a: so- 1&. . TIME------

SOUND SPECTROGRAPH

...... 0\ Figure 9. Flight sounds of Tabanidae (Diptera): The tabanid in flight (top left) produces a complicated sound wave (lower left) which is characterized by the loud pulses resulting from the fast upstrokes. The pulsating nature of the wave produces harmonics with frequencies that are multiples of the wing stroke rate. The sonogram on the right is of the flight sounds of a female Tabanus nigripes beating her wings at progressively lower rates. Frequency (Hz or cps) is figured by the Y axis, and timed by the X axis. The lowest frequency band is the fundamental tone or wing-beat frequency and the remaining frequency bands are harmonics.

Figure 10. The relationship of the wing-beat frequency to harmonics: As the frequency (Hz) of the fundamental tone increases. the harmonic overtones increase at multiples of the fundamental frequency. The frequency scale (Y axis) is the "ruler" prepared from the 50-cps or -Hz calibration lines shown in the sonogram in Figure 9. The X axis shows the range of wing-beat frequencies recorded for Tabanidae. and those reported by Belton and Costello (1979) for mosquitoes.

64 65

Figure 10

, ;;iiOOIJ . : : : .· .. : , 7'· §950' : . : : .· , §1900 : . : : : .. .. , L' !§'850 . . ./ Harmon~ ... : : .. , :s ~"' ~1800 : . .··3rd / ...... , ;;750 :. : . : .. , 2nd / §1700 :. : ...... , ./' 1st : .. ..,, ~ ro:>u ::: : .. · , r./ ::itlUO ::: : .. . , ,,. / §1550 ...... : .· , .: .. , , /, ;;lsoo ..... : . ~ .-[5() .: . .. . ,' _.,/ ~ §i~OO : .. , / ~ ~ 350 .. . ,' /" _...... - E 3oo , ., .. . .. , ..,...,- Fundamental ; 250 ... , ..,, ..,...,- (Wi l'1 a-Beat Freau encv) ~200 ,' _.,/ ~ ~ 150 r..-" ..,...,- ~100 ~ ~so nz 50 100 150 200 250 - 300 350 400 Hz \" TABANIDAE CULICIDAE Figure 11. Average wing-beat rates (cps) and standard deviations calculated for 17 species of Pangoniinae: Sample sizes are given in parentheses after the specific names along the

X axis (~. s Chrysops and i· = Stonemyia). Species are listed in decreasing order of wing beat rates.

66 67

Figure 11

• C. -.;hWJ (l I _...._... s. tranq&dlla (3) ...... c. brunneus Ill c. flav1dus (21 • c . • ,.J'NAJ (11 c. vJtutu (331 c. 1mlu Ill

c. pjkei. (111 c. -•rJ (201 c .. •cqun1 (19) II -...... c. cuc:Juw (21 ... c. nJger (41 --..... c. .i.,unc:tus (3) c. unJvJttMtua 1191 c. gooainotus (191 c. dnctJcornJs (171 c. caJU

0 :il &~-~ ~ ~ :s ~ ~ ~ ! s = Figure 12. Average wing-beat rates (cps) and standard deviations calculated for 22 species of Tabaninae: Sample sizes are given after the specific names along the X axis (Haem. =

Haematooota. ~· = Atylotus. ~ = Hybomitra. and 1· =Tabanus). Species are listed in decreasing order of wing-beat rates regardless of wing length or wet weight.

68 69

Figure 12

r. •tt•ta Ill r. cdena Il l

- 2'. JUgn~•ceu (31

"'· .....t..U (61

r. ~rJ...,.tuJua (171

'J" • nlcJ~.I'OM (141 - •· .UfE1t:JJ:I.a (41 .... • · Jdczocelfl!haJa Ill ..... ~~· (51 r. tr.1Mea.Jae.e (11)

:r. r.UwudtiJ (:;)

•· ainaacaJ• 1271

(I) il !'. IJJ&ll.la

•• .ocS&U• (51 "'· quJ-Jecae.. (24) .. JuJop/1~ (11) !'• .UvrJPH (281 • •. ~....u (1) ____, !'. pualJuo 1161

"· --J• (81 '!". •peru. alllerl (181

A. bJcoJor 161

0 &~ ~ ~ :: ~ ! ~ ~ 2 ~ ~ Figure 13. Sonogram of Chrysops vittatus (female) showing the fundamental tone or wing-beat frequency (Hz or cps) and 5 harmonic overtones. Other frequency bands are overtones at 1/2 the distance between the fundamental and the first harmonic and between each of the other harmonics.

70 71

Figure 13

950 Sth Harmonic --...... 850 t------__ ,__ 4th Harmonic - 3rd He~rmonic ------.

2nd Harmo~~~c~------~~~------~-~ - -

1st Ha rmonic - -···----- Fundamental

Seconds Figure 14. The effect of temperature changes on the wing. beat rates of individual tabanid specimens: A rise in ambient temperature (X axis) of 1°C results in an average increase of 3.4 Hz or cps of the fundamental tone or wing·beat rate (Y axis). Line 1 is from a female Chrysops cincticornis and has a slope of 3.74. Lines 2, 3, 4, and 5 are of f. beameri with slopes of 4, 4.8, 2, and 0.91, respectively. Line 6 is from a female f. vittatus with a slope of 5, and line 7 is of a female Tabanus guinguevittatus with a slope of 2.16.

72 73

Figure 14

7 ~6

2s ~ 30 31 32 33 34 35°C Figure 15. The effect of temperature range and sample size on the presentation of results: These graphs were constructed from the species averages for wing.beat rate (Y axis) and wing length (X axis) of specimens recorded at three different temperature ranges; 101 specimens were recorded at temperatures less than 26°C. 229 specimens between 26 and 28~C. and 89 specimens above 28°C. Note the increased clustering of data points in the 26 to 28°C graph.

74 Figure 15 180 75 170 Temperature Range <26°C + Pangoniinae 160 •• •Tabaninae 150 .. 140 •• * •• 130 • • • • • 120 • • • • • 110 • • • 100 • • 90 180 10 14 18 20 Ill -fr 170 Temperature Range 26 to 28°C ~ 160 • N •• e 15o • • • ~., 140 .·~ • ... + ••• ••• ... 130 • • .8"' 120 • I •• • • • "' 110 -=31 100 180 6 10 14 18 20 170 • Temperature Range >280C 160 • • • • • 150 • • • • 140 • • 130 • • • 120 • • • • • 110 •• 100 vinq 1en9th (mm) 90 • 6 10 14 18 20 Figure 16. The relationship between mean-wing beat rates (Y axis) and mean wing lengths (X axis) of 12 species of Pangoniinae and 20 species of Tabaninae : Pangoniinae are represented by open, starred circles and a dotted regression line with the formula Y = 344.782x-0·464 , and Tabaninae are represented by black dots and correspond to the dashed regression 1i ne 'IIi th the formula Y = 2.88.712x-0· 316 • These lines were calculated from 40 pangonine specimens and 103 tabanine specimens, and the correlation coefficients for both lines are significant to the alpha level of 0.01. Numbers associated with each point

refer· to species and mean values of wing length and wing-beat frequency listed in Table 2.

76 Figure 16

200

175 _,. H" .20 •• % I - -¢: ~150

80 5 6 7 8 9 10 11 12 13 15 16 17 18 19 20 25 Wing Length (mm) Figure 17. Wing-beat rate and wing length relationships of Tabanidae and Culicidae, and Greenewalt's (1962) boundary line: Regression line for Chrysops and Tabaninae are the same as those in Figure 16, however, here the regression line calculated for 13 species of Canadian mosquitoes (Y = 822x-0•725) by Belton and Costello (1979) is also included. Greenewalt's boundary line represents an upper limit for insects for which values of wing length and wing-beat frequency were available in the literature.

78 Figure 17 1000 .. 900 . 800 700 •-means of 600 ··. Tabaninae ··.~ • ••(Qt

'·"~·~7,. ··~? . ""···~~ ·.~ ··.~~ ······ ... ··· ... ·· ... ·· ... ·... 100 90 •········ ... 80 ·.. 70 ·.. ·. 20 30 40 50 60 Figure 18. The effect of increased wing length (X axis) on wing shape (Y axis): The shape factor is the square root of the average wing area divided by the average wing length for each species. Points falling below the regression line represent species with narrower wings relative to species represented by points which fall above the line. Numbers associated with each point refer to species listed in Table 2. Solid points are those of Tabaninae while open starred circles are for Pangoniinae.

80 81

Figure 18

.53

.52 ., <}I <} ,}2 .51 •' •"' ].so ~ l5 i-49 ... e20 t a 27. .48

,}2

.46 •"

Wing Length lmml Figure 19. The relationship of wing length (X axis) to body weight (Y axis): Lines A and D are those calculated by Greenewalt (1962) for birds 3449 0 3376 (Y = 5.31ox0• ) and insects (Y = 2.4817x • ), respectively. Lines Band C were calculated for 2433 Pangoniinae (Y = 4.053sx0• ) (open circles) and Tabaninae (Y = 2.8433x0•3350 ) (closed circles), respectively.

82 Fi r.urc 19

30 ...... ······· ...... • ... ·········;.,. 20 ...... ···· E' 15 ...... ,§...... c ... 0. ... :ii 10 ...... ······ ...J 9 ...... Ol = 8 :!: 7 6

5 80 100 200 300 400 4 6 8 10 20 40 60 Body We ight (mg)

co w SUMMARY

A recording chamber, in which flies were tethered in a fixed position and induced to display flight behavior, was designed and constructed to record the wing beat or flight sounds of horse- and deerflies (Diptera, Tabanidae). A total of 420 specimens, representing 39 species in 6 genera was recorded, sonographed, and analyzed. Elements of tabanid flight sounds as presented in sonograms include the fundamental tone or wing-beat frequency, harmonic overtones which have frequency levels at multiples of the fundamental, occasional non-harmonic overtones, and loudness with an apparent ability of flies to change the intensities of the other elements in sound. Because of the effect of temperature on flight sound, an average increase of 3. 5 cycles per second per one degree centigrade increase in temperature, only recordings of specimens made between 26 and 28°C were used for analysis. Of those parameters measured, wing length had the highest significant correlation to wing-beat frequency. Two regression lines, one for Pangoniinae (Chrysops and Stonemyia) and one for Tabaninae (Haematopota, Atylotus, Hybomitra, and Tabanus), were calculated. Wing beat frequency means for various species were found to have an average standard deviation of 10 cps. The means of a few species were found to deviate from the regression line by more than one standard deviation. These results indicate that a single parameter

84 85

(wing length) is not sufficient for predicting the wing-beat rates of all Tabanidae. Wet weight was also found to be significantly correlated with the wing-beat frequencies of tabanine specimens. The effect of size was also determined: In general, as the wing length increases, wing loading increases and wings become narrower {the shape factor decreases). The expected effects of these scale phenomena initially appear to contradict the observed decrease of wing-beat frequency with increased size. This decreased wing-beat rate, however, is probably due to the resonant mechanical frequency of the wing and wing articulation structures which also tend to decrease with an increase in size. Various species, particularly Chrysops sp., were found to have different wing-loading shape-factor values than other species such as Tabanus sp. of comparable size, and these differences may be used to explain their deviations from the wing length vs. wing-beat rate regression line. Seven of the eight male specimens recorded and sonagraphed had higher wing beat rates than the means of their respective females.

Bog or forest restricted species such as Hybomitra minuscula and ~· difficilis had lower than expected wing-beat rates while pestiferous species found in open areas such as Chrysops callidus and Tabanus quinquevittatus had higher than expected rates. These results suggest possible sexual- and habitat-related behavioral differences which could override the morphological factors influencing the production of sound. APPENDIX A

Collection data for specimens recorded: Genus, species, author, location, number of specimens recorded in parentheses, and date. Number of specimens refers to female Tabanidae unless indicated otherwise.

Pangoniinae: Stonemyia tranguilla (Osten Sacken}: Roaring Plains, Randolph Co., WV, (2 females, 1 male) 4 Aug. 1979. Chrysops beameri Brennan: Cedar Bog, Champaign Co., OH, (1) 30 July 1979, (18) 13 Aug. 1979, (2) 27 Aug. 1979. Chrysops brunneus Hine: Mentor Marsh, lake Co., OH, (3) 18 July 1978. Chrysops callidus Osten Sacken: Rockmill Dam Reservoir, Fairfield Co., OH, {1 reared) 10 May 1978, (5) 5 June 1978; Green Tree Acres. Delaware Co., OH, (6) 15 June 1978; St. Joseph's River, Williams Co •• OH, (2) 20 June 1978; Secrest Arboretum, Wayne Co •• OH, (1) 23 June 1978; Cedar Bog, Champaign Co., OH, (1) 26 June 1978, (1) 2 July 1979, (1) 9 July 1979, (1) 30 July 1979. (1) 27 Aug. 1979.

86 87

Chrysops cincticornis Walker: Rockmill Dam Reservoir, Fairfield Co., OH, (2 reared) 10 May 1978, (1 male, 2 females reared) 20 May 1978, (2 reared) 27 May 1978, (6) 5 June 1978; Cedar Bog, Champaign Co., OH, (2) 26 June 1978. Chrysops cuclux Whitney: Tar Hollow St. Pk., Ross Co., OH, (2) 10 June 1978. Chrysops flavidus Wiedemann: Cedar Bog, Champaign Co., OH, {1) 18 June 1979, (1) 25 June 1979. Chrysops geminatus Wiedemann: Cedar Bog, Champaign Co., OH, (5) 26 June 1978, (3 females, 1 male) 25 June 1979, (1) 2 July 1979, (4) 11 July 1979, (6) 16 July 1979, (1) 23 July 1979. Chrysops impunctus Krober: Cedar Bog, Champaign Co., OH, (3) 2 July 1979, (2) 16 July 1979. Chrysops indus Osten Sacken: Pymatuning Lk., Ashtabula Co., OH, (1) 7 June 1978; St. Joseph's River, Williams Co., OH, {1) 20 June 1978; Cedar Bog, Champaign Co., OH, (1) 2 July 1979. Chrysops macguarti Philip; Secrest Arboretum, Wayne Co., OH, (5) 24 June 1978; Cedar Bog, Champaign Co., OH, (5) 26 June 1978, (1) 2 July 1979, (2) 11 July 1979, (6) 16 July 1979. Chrysops moechus Osten Sacken: St. Joseph's River, Williams Co., OH, (1) 20 June 1979. Chrysops niger Macquart: Rockmill Dam Reservoir, Fairfield Co., OH, (1) reared) 10 May 1978, (2) 5 June 1978; Cedar Bog, Champaign, Co., OH, 25 June 1979. 88

Chrysops pikei Whitney: St. Joseph's River, Williams Co., OH, (3) 20 June 1978; Cedar Bog, Champaign Co., OH, (1) 16 July 1979, (3) 23 June 1979, (2) 30 July 1979; Rockmill Dam Reservoir, Fairfield Co., OH, (1 male reared) 15 June 1978. Chrysops shermani Hine: Cranesville Swamp, Preston Co., WV, (1) 14 Aug. 1978. Chrysops univittatus Macquart: Secrest Arboretum, Wayne Co., OH, (1) 24 June 1978; Cedar bog, Champaign Co., OH, (9) 26 June 1978, (5) 16 July 1979, (1) 30 July 1979, (2) 13 Aug. 1979, (1) 27 Aug. 1979. Chrysops vittatus Wiedemann: Secrest Arboretum, Wayne Co., OH, (10) 24 June 1978; Cedar Bog, Champaign Co., OH, (4) 26 June 1978, (1) 2 July 1979, (2) 11 July 1979, (13) 16 July 1979, (1) 30 July 1979, (2) 13 Aug. 1979.

Tabaninae: Haematopota rara Johnson: Cedar Bog, Champaign Co., OH, (3) 26 June 1978, (2) 2 July 1979; Cranesville Swamp, Preston Co., WV, (1) 5 Aug. 1979. Atylotus bicolor Wiedemann: Cedar Bog, Champaign Co., OH, (1) 26 June 1978, (3 females, 1 male) 30 July 1979, (1) 6 Aug. 1979. Atylotus ohioensis (Hine):Cedar Bog, Champaign Co., OH, (1 male) 25 June 1979, (1) 11 July 1979, (1) 16 June 1979, (1) 23 July 1979, (4) 30 July 1979. 89

Hybomitra difficilis (Wiedemann): Tar Hollow St. Pk., Ross Co., OH, (4) 10 June 1978. Hybomitra lasiophthalma(Macquart): Tar Hollow St. Pk., Ross Co., OH, (1) 10 June 1978; Secrest Arboretum, Wayne Co., OH, (1) 24 June 1978; Cedar Bog, Champaign Co., OH, (7) 26 June 1978, (2) 11 June 1979, (1) 18 June 1979, (1) 25 June 1979, (3) 2 July 1979, (1) 23 July 1979. Hybomitra microcephala(Osten Sacken): Cranesville Swamp, Preston Co., WV, (3) 14 Aug. 1978. Hybomitra minuscula(Hine): Cranesville Swamp, Preston Co., wv. (10) 12 Aug. 1978, (17) 5 Aug. 1979. Hybomitra pechumani Teskey and Thomas: Cranesville Swamp, Preston Co., WV, (1) 5 Aug. 19i9. Hybcmftra sodalis Williston: Cedar Bog, Champaign Co., OH, (1) 25 June 1978, (3) 11 July 1979; Cranesville Swamp, Preston Co., WV, (1) 5 Aug. 1979. Tabanus atratus Fabricius: Cedar Bog, Champaign Co., OH. (1) 13 Aug. 1979. Tabanus calens linnaeus: Delaware lk. Public Hunting and Fishing Area, Delaware Co., OH, (1) 22 Aug. 1978; Henry Co., OH, (1) 23 Aug. 1978. Tabanus nigrescens Palisot de Beauvais: Cedar Bog, Champaign Co., OH, (2) 16 July 1979, (1) 6 Aug. 1979. 90

Tabanus nigripes Wiedemann: Cedar Bog, Champaign Co., OH, (4) 26 June 1978, (4) 2 July 1979, (2) 16 July 1979, (8) 23 July 197g, (6) 30 July 1979, (2) 6 Aug. 1979, (1) 13 Aug. 1979. Tabanus pumilus Macquart: Cedar Bog, Champaign Co., OH, (2) 26 June 1978, (2) 2 July 1979, (7) 11 July 1979, (3) 16 July 1979, (1) 23 July 1979. Tabanus quinguevittatus Wiedemann: Tipton lane, Scioto Co., OH, (3 females, 2 males) 14 June 1978; Cedar Bog, Champaign Co., OH, (1) 26 June 1978, (2) 11 July 1979, (4 females, 2 males) 23 July 1979, (2) 30 July 1979, (4) 6 Aug. 1979, (3) 13 Aug. 1979. Tabanus reinwardtii Wiedemann: Rockmill Dam Reservoir, Fairfield Co., OH, (1 male, 1 female reared) 19 June 1978; Cedar Bog, Champaign Co., OH, (1) 30 July 1979. Tabanus sackeni Fairchild: Cedar Bog, Champaign Co ., OH, (1) July 1979, (1) 6 Aug. 1979, {2) 13 Aug. 1979, (2) 27 Aug. 1979. Tabanus similis Macquart: Cedar Bog, Champaign Co., OH, (1) 18 June 1979, (1) 11 July 1979, {1) 16 July 1979, (2) 30 July 1979, (2) 6 Aug. 1979, (1) 13 Aug. 1979. Tabanus sparus milleri Whitney: Secrest Arboretum, Wayne Co., OH, {1) 14 June 1978; Cedar Bog, Champaign Co., OH, (1) 26 June 1978, {1) 11 June 1979, (1) 15 June 1979, (1) 2 July 1979, 91

(2) 11 July 1979, (4) 16 July 1979, (5) 23 July 1979, (3) 30 July 1979. Tabanus sulcifrons Macquart: Delaware Lk. Public Hunting and Fishing Area, Delaware Co., OH, (1) 22 Aug. 1978; Cedar Bog, Champaign Co., OH, (1) 16 July 1979, (1) 30 July 1979, (8) 6 Aug. 1979, (3) 13 Aug. 1979. Tabanus superjumentarius Whitney: Cedar Bog, Champaign Co., OH, (6) 26 June 1978, (2) 25 June 1979, (5) 11 July 1979, (3) 23 July 1979, (1) 13 Aug. 1979. Tabanus trimaculatus Palisot de Beauvais: St. Joseph's River, William Co., OH, (1) 20 June 1978; Secrest Arboretum, Wayne Co., OH, (2) 24 June 1978; Cedar Bog, Champaign Co., OH, (2) 26 June 1978, (1 male) 25 June 1979, (1) 2 July 1979 , (4) 11 July 1979, (3) 16 July 1979, (1) 23 July 1979 , (2) 30 July 1979. Tabanus vivax Osten Sacken: Roaring Plains, Randolph Co., WV, (1) 4 Aug. 1979. APPENDIX B Flight Mode of Diptera

There are two extreme modes of flight to consider: no forward speed, only flapping, and high speed glide without flapping. All actual cases will lie in between these two modes. Analogous to helicopter-rotor analysis, one can express the flight state in terms of an advanced ratio, ~=

_ forward velocity (v) ~ - maximum flapping velocity (Wmax)

If ~ = 0, then the insect has no forward speed.

If~ = ~. the insect glides without flapping.

If~ = 1, the maximum tip speed equals the forward velocity. A typical advanced ratio for an insect flying at a speed of v = 15 feet/sec., with a wing span of 2 inches, a wing-beat frequency of 100 cps (628 rad/sec), and a wing stroke angle of 80 degrees (1.396 radians) is~= v/Wmax = 15/73 = 0.205 (Wmax = 1.396·1/12·628). It is thus shown that~ is considerably smaller than 1, and therefore using

~ = 0 is an acceptable approximation of dipteran flight.

92 APPENDIX C Sa10p1e c:alc:ulaUen of the effective aerodynallic c:~nter; Chrysops ~

- Ci(IID) C;CIIIIVWSL) (i·'U2 (i·'t)3 (1-1>)~ (i·'s)2ci a1(m) At (IIIIV'WSL) •t-'

10 1.4 1.59 90.25 157.38 1~3.23 143.50 0.7 0.80 0.09 U.915 t--- t-- t--- 6612.51 943.43 260.03

(EACJ 6682.58 0.78, 70.8,, or 6.23 mm from the tegulum along the 5 943.43 Wing-Span Line (WSL).

(EAC) ~ 0.027, 2.76,, or 0.24 mm in front of the Wing-Span c 943.43 Line (WSL).

93 BIBLIOGRAPHY

Anthony, D. W. 1960. Tabanidae attracted to an U.V. light trap. Fla. Ent. 43(1): 77-80. Bailey, N. S. 1948. The hovering and mating of Tabanidae (Diptera). Ann. Entomol. Soc. Amer. 41(4): 403-412. Bailey, N. S. 1948. Hovering males of Hybomitra cincta (Fabr.). Psyche 55(4): 178-180. -- Belton, P. and R. A. Costello. 1979. Flight sounds of the females of some mosquitoes of Western Canada. Ent. Exp. &App. 26: 105-114. Bennet-Clark, H. C. and A. W. Ewing. 1968. The wing mechanism involved in the courtship of Drosophila. J. Exp. Biol. 49: 117-128. Bennet-Clark, H. C. and A. W. Ewing. 1970. Chapter 19. The love song of the fruit fly. (pp. 181-187) in The Insects, T. Eisner and E. 0. Wilson, ed., W. H. Freeman and~. San Francisco. Blickle. R. L. 1955. Observations on habits of Tabanidae. Ohio J. Sci. 55(5): 308-310. Bonhag, P. F. 1949. The thoracic mechanism of theadult horsefly (Diptera: Tabanidae). Cornell Univ. Ag. Exp. Sta. Memoir 285. Cade, W. 1975. Acoustically orienting parasitoids: Fly Phonotaxis to cricket song. Science 190: 1312-1313. Chadwick, L. E. 1939. Some factors which affect the rate of movement of the wings in Drosophila. Physiol. Zoo. 12: 151-160. Chapman, R. F. 1971. The Insects: Structure and Function. America Elsevier Publishing!Co., Inc. New York. 819 pp. Costello, R. A. 1974. Effect of environmental and physiological factors on the acoustic behavior of Aedes ~i (L.) (Diptera: Culicidae). Ph.D. Thesis, Simon Fraser Un1v. Cowan, B. D. and W. M. Rogoff. 1968. Variation and heritability of responsiveness of individual male house flies, Musca domestica, to the female sex Pheromone. Ann. Entomol. Soc~ 61: 1215-1218.

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Craig, W. 1944. The twilight ceremonies of horse flies and birds. Science 99: 125-126. Drees, B. M., L. Butler, and L. L. Pechuman. In Press. The horse and deer flies of West Virginia; An illustrated key (Diptera: Tabanidae). Biological Bulletin, West Virginia Exp. Sta., West Virginia Univ., ~1organtown. Duke, B. 0. L., W. Crewe and W. N. Beesley. 1956. The relationship between the size of the blood-meal taken in by Chrysops silacea, the development of the fly's ovaries, and the deve opment of the microfiliariae of loa loa taken in with the blood-meal. Ann. Trap. Med. and Parasit. ;D: 283-290. Ehrman, L. 1959. The antennae of Drosophila females. Evolution 13: 147. Evans, H. E. 1966. life on a little Known Planet. E. P. Dutton and Co., Inc. New YorK. 3T8_p_p-.------Farb, P. 1962. The Insects. Time Incorporated. New York. 172 pp. Fletcher, N. H. 1978. Acoustical response of hair receptors in insects. J. Camp. Physiol. 127: 185-189. Gaul, A. T. 1951. A relationship between temperature and wing beats. Bull. Brooklyn Entomol. Soc. 46: 131-133. Gooding, R. H. 1972. Digestive processes of haematophagous insects. I. A literature review. Quaestiones Entomologicae 8: 5-60. Greenewalt, C. H. 1962. Dimensional relationships for flying a.nimals. Smithsonian Misc. Coll. 144(2): 1-46. Haddow, A. J., P. S. Corbet, J. D. Gillett, and others. 1961. Entomological studies from a high tower in Mpanga Forest, Uganda. Trans R. Entomol. Soc. London 113: 249-368. Hagmann, L. E., G. W. Barber, E. B. Starnes, and 0. Starnes. 1947. Evening flight habits of a male Tabanid. Ent. New 59(10): 257-258. Haseman, l. 1947. The courting flights of Tabanids. Science 97: 285-286.

Haskell, P. T. 1961. Insect Sounds ~: Aspects of Zoology series. Witherby, london. 189 pp. Heinrich, B. and G. A. Bartholomew. 1972. Temperature control in flying moths. Sci. Amer. 226(6): 70-77. 96

McAtee, W. L. 1911. Facts in the life history of Goniops chr~socoma (Oiptera: Tabanidae). Proc. Entomol. Soc. Wash. 13: 21-2 • Miller, L. A. 1951. Observations on the bionomics of some Northern species of Tabanidae. Can. J. Zoo. 29: 249-267. Mosier, C. A. and T. E. Snyder. 1918. Notes on gad flies in the Florida everglades. Proc. Entomol. Soc. Wash. 20(6): 115-126. Nachtigall, W. 1968. Insects in Flight. McGraw-Hill Book Co. New York. 153 pp. Nash, R. and H. C. G. Ross. 1977. A note on the hovering behavior of Haematopota pluvialis (L.). Entomologists Gazette 28: 267. Oldroyd, H. 1964. The Natural History of Flies. W. W. Norton & Co., Inc. New York. 324 pp. Philip, C. B. 1931. The Tabanidae (horseflies) of Minnesota with special reference to their biology and taxonomy. Univ. Minn. Agr. Sta. Tech. Bull. 80: 1-132. 97

Popham, E. J., M. J. Parr, and V. Chowdhury. 1978. Specific differences in tsetse fly sounds and their behavioral significance. Experimentia 34(9): 1151-1154. Pringle, J. W. S. 1957. Insect Flight. Cambridge Univ. Press. london. 132 pp. Roberts, R. H. 1971. Effect of amount of co, on collection of Tabanidae in Malaise traps. Mosquito Ne~s (31(4): 551-558. Roberts, R. H. 1975. Altitude distribution of Tabanidae as determined by Malaise trap collections. Mosquito News 36(4): 518-520. Roth, L. M. 1948. A study of mosquito behavior. An experimental laboratory study of the sexual behavior of Aedes aegypti (l.). Amer. Mid. Nat. 40: 265-352. -- Schwardt, H. H. 1932. The life histories of two horseflies. Ann. Entomol. Soc. Amer. 25(3): 631-637.

Schwardt, H. H. 1934. Biological notes on Gonio~s chr,socoma (Diptera, Tabanidae). J. Kan. Entomol. Soc. (3): 3-79. Schwardt, H. H. 1936. Horseflies of Arkansas. Univ. Kan. Agr. Exp. Sta. Bull. 332: 1-66. Sharp, J. l. and J. C. Webb. 1977. Flight performance and signaling sound of irradiated or unirradiated Anastrepha suspensa. Proc. Hawaiian Entomol. Soc. 22: 525-532. Sotavalta, 0. 1947. The flight-tone (wing stroke frequency) of insects (Contributions to the problem of insect flight I.). Acta Entomol. Fennica 4: 1-114. Stone, A. 1930. The bionomics of some Tabanidae (Diptera) . Ann. Entomol. Soc. Amer. 23: 261-304. Tashiro, H. and H. H. Schwardt. 1949. Biology of the major species of horse flies of Central New York. J. Econ. Entomol. 42:269-272. Thompson, D. W. 1952. On Growth and Form. Vol. 1. University Press, Cambridge, England.------Thorsteinson, A. J. 1958. The orientation of horseflies and deerflies; I. The attractance of heat to tabanids. Entomol. Exp. &Appl. 1: 191-196. Ubel, E. C., E. P. Sonnet, B. A. Bierl, and R. W. Miller. 1975. Sex pheromone of the stable fly: isolation and preliminary identifica tion of compounds that induce mating strike behavior. J. Chemical Ecol. 1: 377-385 . 98

Waldron, I. 1964. Courtship sound production in two sympatric sibling Drosophila species. Science 144: 191-192. Webb, J. C., J. L. Sharp, D. L. Chambers and J. C. Benner. 1976. Acoustical properties of the flight activities of the Caribbean fruit fly. J. Exp. Biol. 64: 761-772. Webb, J. C., J. L. Sharp, D. L. Chambers, J. J. McDow, and J. C. Benner. 1976. Analaysis and identification of sounds produced by the male Caribbean fruit fly, Anastrepha suspensa. Ann. Entomol. Soc. Amer. 69: 415-420. Webb, J. L. and R. W. Wells. 1924. Horse-flies: biologies and relation to Western agriculture. U.S.D.A. Bull. 1218: 1-36. Williams, C. M. and R. Galambos. 1950. Oscilloscopic and stroboscopic analysis of the flight sounds of Drosophila. Biol. Bull. (Wood's Hole) 99: 300-307. Wilson. B. H. 1967. Feeding, mating, and oviposition studies of the horseflies Tabanus lineola and T. fusciostatus (Diptera, Tabanidae). Ann. Entomol. Soc.-Amer. 60(5): 1102-1106. Wilson, B. H., N. P. Tugwell and E. C. Burns. 1966. Attraction of Tabanids to traps baited with dry ice under field conditions of Louisiana. J. Med. Entomol. 3(2): 148-149. Wishart, G. and D. F. Riordan. 1959. Flight responses to various sounds by adult males of Aedes aegypti (L.) (Diptera: Culcidae). Canad. Ent. 91: 181-191. Yelizarov, Yu. A. and S. Yu. Chayka. 1978. Ultrastructure of the olfactory sensilla of horse flies (Diptera, Tabanidae) . Entomol. Review 56(2): 32-38. Errata

The first, bookmarked, version of this thesis in this PDF was reproduced from a reduced-sized copy received from University Microfilms; the second version was derived from a full-size (but, unfortunately only 2-color, 1-bit) scan supplied to me by Bart Drees on 11 January 2013; I cleaned up that copy (noise removal, de-skewing, image enhancement), but the following corrections were made only to the Universi- ty Microfilms copy; the second, full-size version is exactly as printed.

————————————————

The following corrections have been made without notification in the text:

• “thoracinus” was rendered as “thorasicus” • “sulcifrons” was sometimes rendered as “sulcifrous” • “aurilimba” was sometimes rendered as “aurilimbus” • “illota” was sometimes rendered as “illotus” • “hematophagous” was rendered as “haematophagus” • “occasionally” was sometimes rendered as “occassionally” • “minuscula” was rendered as “miniscula” • “sonogram” was sometimes rendered as “sonagram” and “sonograph” as “sonagraph” • “Chrysops” was sometimes rendered as “Chyrsops” • “Haematopota” was sometimes rendered as “Haematoapota” • hyphens have been added to phrases such as “field collected late instar larvae” (changed to “field- collected late-instar larvae”), and wing beat rate control” (to “wing-beat-rate control”) • for discrete variables, “less” was changed to “fewer” • “bloodmeal” occurs as both one and two words; I have used the 1-word format • “Pangoniinae” was sometimes rendered as “Pangoninae” • “pluvialis” was rendered as “plufialis” • “trimaculatus” was sometimes rendered as “trimaculata” • “Champaign” was sometimes rendered as “Champaing” • instances of “irregardless” [sic] were changed to “regardless” • the gender of some of the species names in Chrysops was changed from feminine to masculine • some species of Hybomitra (e.g. affinis) were incorrectly assigned to Tabanus • commas were sometimes used where semicolons were required, leading to run-on sentences • “effect” and “affect” were sometimes confused

The following paper was omitted from the bibliography; it was cited on p. 4 (in error as “Merchand”) where, as well, “abdominal” was rendered as “abdnominal”.

Marchand, W. 1918. The evolution of the abdominal pattern in Tabanidae. Transactions of the American Entomological Society, 44: 171–179 + 1 plate.

Note as well that all instances of supposed synonymies were reported incorrectly. For example, we have

“Hybomitra frontalis (Walker) (= T. septentrionalis)” which implies that the correct name is “septentrionalis” when, in fact, septentrionalis is the synonym. The author was trying to indicate that the name under which the observations were published is no longer valid, so the syntax should have been

“Hybomitra frontalis (Walker) (as Ta. septentrionalis)”.

Stephen M Smith, Department of Biology, University of Waterloo, Waterloo, ON Canada N2L 3G1 [email protected]; [email protected] 26 December 2012; updated 11 January 2013 THE BIOACOUSTICS OF TABANIDAE

ABSTRACT. The behavioral mechanism in horseflies and deer flies

Tabanidae) for sexual recognition is largely unknown. However, indirect

evidence cited in the literature on tabanid behavior suggests that sound may

also play an important role in thisa behavior. Standardized laboratory

recordings of wing sounds from 420 tethered tabanid specimens representing 39 species in 6 genera from Ohio and West Virginia were sonographed and analyzed.

Elements of wing sounds, including the fundamental tone, harmonics, and non

harmonic overtones, are described. A significant correlations was found to occurr between wing length and wing beat frequency, although the regression

line for the superfamily Tananinae differed from that of the Pangoniinae. Other

physical parameters, including wing area, wet weight, wing loading, and wing

shape, and their possible influences on sound production are discussed.

However, the conclusion is drawn that no single parameter can successfully be

used to predict the sounds produced by all tabanid species. The influence of

secondary physical parameters and more importantly, sexual and habit related behavioral requirements for flight appear to have a modifying effect on the sounds produced.

Key words: Diptera, Tabanidae, acoustics, behavior THE BIOACOUSTICS OF TABANIDAE (DIPTERA)

DISSERTATION

Presented in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in the Graduate School of The Ohio State University

By Bastiaan Meijer Drees. B.A., M.S.

* * * * *

The Ohio State University

1980

Reading Committee: Approved By Dr. Donald E. Johnston Dr. Glen R. Needham dviser Dr. Donald J. Borror Departmen of Entomology Dr. Willard C. Myser THE BIOACOUSTICS OF TABANIDAE (DIPTERA) By Bastiaan Meijer Drees, Ph.D. The Ohio State University, 1980 Professor Donald E. Johnston, Adviser

The behavioral mechanism in horse flies and deer flies (Diptera, Tabanidae) for sexual recognition is largely unknown, and the lack of this information has prevented researchers from successfully mating these insects in captivity. Undoubtedly, habitat specialization and mating time and location, together with vision, play major roles in bringing the sexes together. However, much indirect evidence cited in the literature on tabanid behavior suggests that sound may also play an important role in this behavioral sequence. Recordings of wing sounds from 420 tabanid specimens representing 39 species in 6 genera from Ohio and West Virginia were sonographed and analyzed. Elements of wing sounds, including the fundamental tone, harmonics, and non-harmonic overtones, are described. Techniques for collecting specimens, including an aerial net and a modified Malaise trap baited with a shiny black sphere and dry ice, were biased to collect female Tabanidae in search of blood meals. The consistent

l 2

treatment of specimens throughout the collecting and recording procedure was assumed to have standardized the behavioral reactions of individual specimens to the extent that results would indicate the relative differences in sound production among the species recorded. Specimens were individually tethered to a fixed rod and induced to disply flight behavior in a recording chamber. The ambient temperature, date and time of day were recorded along with the flight sounds. Specimens were then freeze-killed, weighed and their wings were ranoved in order to accurately determine the length, chord, area, and effective aerodynamic center. Comparisons of sounds produced by different species were restricted to those specimens recorded between 26 and 28°c. A significant correlation was found to occur between wing length and wing beat rate or fundamental, although the regression line for the superfamily Tabaninae (Haematopota, Atylotus, Hybomitra, and Tabanus) differed from that of the Pangoniinae (Chrysops and Stonemyia). Other physical parameters, including wing area, wet weight, wing loading, and wing shape, and their possible influences on sound production are also discussed. However, the conclusion is drawn that no single parameter (i.e. wing length) can successfully be used to predict the sounds produced by all tabanid species. The influence of secondary physical parameters and more importantly, sexual and habitat related behavioral requirements for flight appear to have a modifying effect on the sounds produced. 3

The conclusion that flight sounds of Tabanidae have a biological significance can not be substantiated from the data collected. However, the potential for certain morphologically similar species and individuals to produce different sounds has been documented. Thus, a biological role of sound in tabanid sexual behavior still remains a possibility. Moreover, the results of this investigation may aid researchers in describing the sounds of other insects where flight sounds are known to be biologically significant, and in determining which morphological, physiological, or ethological factors most influence the sounds produced. Copyright by Bastiaan Meijer Drees, Ph.D. 1980 ACKNOWLEDGEMENTS

flight. I am also indebted to Professor Donald J. Borror for the time and effort he gave in teaching me the fundamentals and techniques of bioacoustics, and to Dr. L. L. Pechuman of Cornell University for his continued assistance with the difficult dipterous family, Tabanidae. Special thanks must also be given to Professor Linda Butler of West Virginia University for giving me a broad base of entomological knowledge and the enthusiasm to pursue my interests.

I have enjoyed working with my examination committee members,

Dr. Glen R. Needham and Professor Willard C. Myser and I thank them for undertaking a project which was slightly out of the ordinary. Other members of The Ohio State University faculty who have had a profound influence on my years as a doctorate candidate include, Dr. D. J. Horn, Dr. G. Ekis, Dr. D. L. Denlinger, Dr. C. A. Triplehorn, Dr. G. W. Wharton, Dr. W. A. Foster and Dr. W. C. Rothenbuhler. Day to day

ii existence in Columbus, Ohio was possible and even enjoyable only because of the close friendships and support of my fellow graduate students including Dr. Dan Potter, Dr. Jay Bradfield, Beth Lenoble, Maury Walsh, Greg Walker, Lucille Antony, Connie Rogers, Larry Ross, Ann Gnagey, and Rick Helmich. Finally, I wish to thank the two women in my life: my mother, Jacoba Meijer Drees, and my wife-to-be, Carol Frost, to whom this work is dedicated.

iii VITA

June 28, 1952 Born, Amsterdam, Netherlands 1974 B.A., Biology with minors in Chemistry and Art, West Virginia University, Morgantown, WV. 1974-1976 ...... Laboratory Technician, curator of the Rhopalocera and Tabanidae sections of the Insect Museum, and application of green house pest control in the Horticulture Greenhouse for the Department of Entomology, West Virginia University, Morgantown, WV . 1975-1976 ...... Insect Specialist, identifications and control reconmendations, assisting Dr. J. F. Baniecki, West Virginia Cooperative Extension Service, West Virginia University, Morgantown, WV. 1976 Andrew Delmar Hopkins Scholarship in Entomology, West Virginia University, Morgantown, WV. 1976 M.Sc., Entomology, West Virginia University, Morgantown, WV. 1977 Teaching Associate, Economic Entomology, The Ohio State University, Columbus, OH. 1977-1979 Ohio's Survey Entomologist, in cooperation with the United States Department of Agriculture, the Ohio Department of Agriculture, the Ohio Agr i cultural Research and Development Center, and the Ohio Cooperative Extension Service, The Ohio State University, Columbus, OH. 1979 ...... Teaching Associate, General Biology, Department of Zoology, The Ohio State University, Columbus, OH .

iv 1979 Administrative Assistant and insect specialist for Dr. R. L. Miller, Ohio Cooperative Extension Service, The Ohio State University, Columbus, OH. 1979-1980 ...... Teaching Associate, Insect Morphology, Economic Entomology, and General Entomology, Department of Entomology, The Ohio State University, Columbus, OH. 1980 Instructor, Biology- The World of Insects, Urban Extension and Community Programs, The Ohio State University, Columbus, OH. 1980 Ph.D., Entomology, The Ohio State University, Columbus, OH.

PUBLICATIONS Baniecki, J. F., and B. M. Drees. 1979. General Leaf Feeding Caterpillars, Pest Infonnation Series 87. Cooperative Extension Service, West Virginia University, Morgantwon, WV. 1976. Ants and their control. Pest Information Series 95. Cooperative Extension Service, West Virginia University, Morgantown, WV. 1976. Fleas and their control. Pest Infonnation Series 96. Cooperative Extension Service, West Virginia University, Morgantown, WV.

Drees, B. M. 1977 . .:!..!!. The Cooperative Plant Pest Report 2(15-36). APHIS-PPQ, United States Department of Agriculture, Hyattsville, MD. Citations from the 1977 Ohio Cooperative Economic Insect Report {1-26). --

1978 . .:!..!!. The Cooperative E.!.il.!!.!. Pest Report 3(16-36). APHIS PPQ, United States Department of Agriculture, Hyattsville, MD. Citations from the 1978 Ohio Cooperative Economic Insect Report (1-26). ~ Drees, B. M. and L. Butler. 1978. Rhopalocera of West Virginia. J. Lepidopterist's Society 32(3):192-206. Clement, S. L., G. Szatmari-Goodman, and B. M. Drees. 1979. The status and control of the Ohio corn rootworms. Ohio Report 64(1): 8-10. v Drees, B. M., L. Butler, and L. L. Pechuman. _!!!.press. The horse flies and deer flies of West Virginia; An illustrated key (Diptera Tabanidae). Biological Bulletin, West Virginia Experiment Station West Virginia University, Morgantown, WV.

FIELDS OF STUDY Major field: Entomology Areas of Specialization: Biology of Rhopalocera and Tabanidae, insects of economic importance, and insect behavior.

vi TABLE OF CONTENTS

Page ACKNOWLEDGEMENTS ii VITA • • • • • • iv LIST OF TABLES ix

LIST OF FIGURES x INTRODUCTION . . . l Literature Review of Tabanid Sexual Behavior and Rationale for Investigating the Sounds of Tabanid Flight . 2 METHODS AND MATERIALS • • 11 Collection Techniques . 11 Recording Techniques...... 12 Wing Modifications or Mutilations 15 Temperature Modifications . 15 Sonagrams ...... 16 Loudness ...... 17 Anatomical Measurements . 17 Wet Weight •. 17 Wing Slides. 18 Wing Length. 18 Chord ..... 18 Wing Area. . . 19 Wing Loading ...... 19 Effective Aerodynamic Center .. 19 RESULTS AND DISCUSSION ...... 23 Elements of Tabanid Flight Sound. . 23 Temperature and Sound • . . . . . • ...... 25 The Effect of Wing Dimensions, Wet Weight and Wing Loading on Flight Sound . • . . • . . • . . 28 Wing Length •...• , ...... 31 Chord. . . . . • ...... 32 Wing Area ...... 32 Effective Aerodynamic Center . 33

vii Page

Wet Weight ...... 35 Wing Loading ...... 37 Loudness or Sound Intensity ... . 41 Sexual Differences of Tabanid Sound .. 42 Relation of Wing Beat Rate to Habitat . 43 Concluding Remarks. 45 SUMMARY. 84 APPENDIX A. Collection Data for Specmens Recorded 86 B. Flight Mode of Diptera 92 C. Sample Calculation of the Effective Aerodynamic Center. 93 BIBLIOGRAPHY ...... 94

viii LI ST OF TABLES

Table Page 1 Observations of Tabanid "Courtship" Flights ... 6 2 Means, Standard Deviations, and Sample Sizes for the Wing lengths, Wing Areas, Wet Weights, Wing Loads and Wing Beat Frequencies Between 26 and 28 0 C for Thirty-nine Species of Tabanidae .... 29

3 Factors Influencing the Sounds of Tabanidae (Di ptera) ...... 47

ix LIST OF FIGURES

Figure Page 1 Container used for rearing field collected late i nstar ta bani d larvae ...... 48

2 Two dimensional modified Malaise trap baited with dry ice and a shiny black sphere for field collecting adult Tabanidae...... 50

3 Recording chamber - top view with lid removed and leaning against one side ...... 52

4 Specimen holder, constructed of 1/4 in. plexiglass and 1/8 in. diam. plexiglass rods. 54

5 The outline of a tabanid wing. 56

6 Chrysops cincticornis attached to the tethering rod with rubber cement, resting on the trap door . . . . . 58 7 Chryso\s cincticornis in typical attitude of flight after osing ground contact with the trap door 58 8 Sound production . . . . . 60 9 Flight sounds of Tabanidae (Diptera) 62 lO The relationship of the wing beat frequency to harmonics...... 64 11 Average wing beat rates (cps) and standard deviations calculated for 17 species of Pangoniinae ...... 66 12 Average wing beat rates (cps) and standard deviations calculated for 22 species of Tabaninae ...... 68 13 Sonogram of Chrysops vittatus (female) showing the fundamental tone or wing beat frequency (Hz or cps) and 5 hannonic overtones ...... 70

x Figure Page 14 The effect of temperature changes on the wing beat rates of individual tabanid specimens...... 72 15 The effect of temperature range and sample size on the presentation of results...... 74 16 The relationship between mean wing beat rates (Y axis) and mean wing lengths (X axis) of 12 species of Pangoniinae and 20 species of Tabaninae. . . . . 76

17 Wing beat rate and wing length relationships of Tabanidae and Culicidae, and Greenewalt's (1962) boundary line...... 78

18 The effect of increased wing length (X axis) on wing shape (Y axis) ...... 80 19 The relationship of wing length (X axis) to body weight (Y axis)...... 82

xi INTRODUCTION

Since Roth (1948) demonstrated conclusively that male Aedes aegypti were attracted to the sound produced by the flight of the female, bioacoustically and ethologically oriented entomologists have been searching for biological significance of the noises produced by the wing movements of other Diptera. Much work has been done with Culicidae (Costello, 1974); Wishart and Riordan, 1959), Drosophila (Williams and Gambos, 1950; Sharp et al., 1975; Bennet-Clark and Ewing, 1968 and 1970; Waldron, 1964; and Webb et al., 1976), Tephritidae (Sharp and Webb, 1977), and Glossina (ICIPE, 1974; Popham et al., 1978). Other authors have begun to describe the sounds of related species in search of acoustical isolation or sounds which can be played back to members of the same or opposite sex to observe behav i oral responses. Sounds of related species may also have some taxonomic value. Asilid flight sounds have thus been described by Lavigne and Holland (1969), and more recently the sounds of 13 species of Canadian mosquitoes have been described by Belton and Costello (1979). The objective of the research presented here is to describe the flight sounds of species of horse and deer flies (Diptera, Tabanidae) with a consideration for the factors which influence the sounds produced. 2

Literature Review of Tabanid Sexual Behavior and Rationale for Investigating the Sounds of Tabanid Flight The ability for an organism to perceive and respond to environ mental stimuli is essential for survival. Since "species" may be defined as an ecological, reproductively isolated unit, an important behavioral activity of members of a species is mate location leading to copulation. This is the process of sexual recognition, not to be confused with sexual isolation. Mechanisms of sexual recognition vary greatly and are not documented for the majority of existing organisms. Descriptions of the phenomenon of sexual recognition are highly desirable not only in light of the natural history of organisms, but also to facilitate the breeding of species in captivity making them available for more extensive and controlled scientific research. No one has successfully been able to induce Tabanidae to mate in captivity (Schwardt, 1932, 1936, Philip 1931; Hafez et al. 1971), although many species have been reared from egg to adult. Tabanidae are considered to be one of the more important groups of haematophagus insects for which adequate control measures have not been achieved. These facts emphasize the desirability of understanding sexual recognition mechanisms for this family. Sexual recognition may be defined as the process by which one sex recognizes and proceeds to mate with the other sex of the same species. Sexual isolation may be defined as "behavioral barriers to hybridization between species or populations" (Manning, 1972). Both concepts always apply after evolution has progressed during a period of reproductive isolation. The concern here is only with the adults 3 of sympatric species because sexual isolation must be supported by the evolution of highly specific signals which enable adults to recognize the opposite ·sex of their own species. These signals are emitted by one sex and perceived by another and are responsible for the low incidence of hybridization found in natural conditions. In many insects and probably in the Tabanidae, sexual recognition is especially important for females. Males can usually mate several times in their lifetime but females mate only once (Manning, 1972). The sexual isolation and recognition mechanisms are actually genetic differences between species expressed phenotypically. When sexual recognition signals are to be employed, these signals must be produced and perceived by morphological and behavioral signal producing and receiving structures. Signal perceiving structures may involve the senses of taste, touch, smell, vision and sound. Tabanids have been shown to possess structures which can detect all of the senses except sound (Lall, 1969; Wilson, 1966; Yelizarov and Chayka, 1978; Anthony, 1960; Oldroyd, 1964; Roberts, 1971; Thornstein, 1958). Signal producing structures may stimulate one or several of the sense structures and operate in a particular sequence. Obviously, the senses of touch (tactile sense) and taste (gustatory sense) are involved when the flies are already together and therefore, cannot be responsible for the attraction of the two sexes from a distance. And, although these are probably important in the final stages of copulation, it would be a behavioral disadvantage to spend much energy to pursue and contact other species before locating a mate. Pheromones 4

may also play an important role in sexual recognition of Diptera (Cowan and Rogoff, 1968; Ubel et al., 1975). Tabanidae rely heavily on visual clues for host detection, oviposition sites, and habitat recognition. Discrimination between shapes, sizes, light intensities, colors, and movement is probable because of the well developed compound eyes of tabanids (Philip, 1931), but whether vision alone accounts for species recognition is debatable. Tabanid species vary greatly in size, ranging from about 4 to 35 mm in length. Obviously, the male of a small species will not approach much larger species to attempt copulation. Several members of the family are very brightly colored. Hybomitra cincticornis is a striking example with its bright orange basal abdominal segments contrasting with the black coloration of the rest of the body. Coloration is especially well developed in tropical regions, where some tabanids are mimics of Hymenoptera as a result of modifications in form and color. The shiny metallic coloration of some tropical species could play a role in visual recognition between species. However, the majority of tabanid species are not brightly colored, but are rather dull and only subtly different in abdnominal (Merchand, 1918), eye (Daecke. 1906), or wing patterns (Brennan, 1935). This is especially true of many syrnpatric species. It seems highly unlikely that these species can recognize their mates by color or shape alone, especially at a distance. Time of mating, mating habitat, flight height (Roberts, 1975) and flight velocities may be important species recognition signals which are visually perceived. 5

It is appropriate here to discuss in detail what is already known of tabanid sexual behavior, before continuing the discussion of the role of vision. Male Tabanidae have long been known to hover at certain times of the day in specific locations (Table 1). However, many authors express doubt as to whether these are in fact "courtship" flights (Oldroyd, 1964; Craig, 1944; Evans, 1966). On the other hand, there exists much literature concerning these flights and on a few occasions, matings have actually been observed during the swanning period (Table 1). If the hovering behavior of males is in fact a courting flight, mating times and locations are highly specific and may serve as a species isolating mechanism (i.e. Tabanus thorasicus and T. insignis in the rain forests of Uganda - see Table 1). Behavior during hovering flights seems to involve territoriality while in other species, many males will hover together in a loose swarm (Bailey, 1947; 1948; Evans, 1966). With Hybomitra cincta "hovering is an individual affair and usually no more than one or two males (are) seen so engaged at the same time . On a few occasions when two or three (are) found hovering together, they (are) always some yards apart" (Bailey, 1948). Bickle (1955), in describing the hovering of Tabanus (i.e. Hybomitra) aurilimba, explains that "when another insect flew near, the fly would make a 1 pass 1 at the intruder, return to the same location and continue to hover. 11 Territoriality may be a necessary requirement in sound attraction because "sound responses work better if there are no other individuals to cause confusion ... attraction of a male to a female can only occur in relative isolation and not amongst a crowd or swann" (Haskell, 1961; from Oldroyd, 1964). TABLE 1 IJbsl'rvattons of Tabanid "Courtship" Fl lghts

Flight topulatton Species Otiserver Fl i~ht Oates Time of Day Heights Observed

Tabanus americanus Hasemann (1943) 9 Sept - 15 Sept 7:00 p.m. 3-5 ft. No --ig:1 g~.,teus) 30 3 ft. candles !· ""'ericanus Hagmann f't 11 I . 10 Aug • 12 Aug 7: 20-8: 10 p.m. 2-5 ft . Yes -rgTgant.eus) (1947) to 20 ft. T. sulcl frous Hasemann (1943) 27 July - 2 Sept 5:30a .rn. 30 ft. No 1 to 3 or 5 ft. above trees candles. 20-25 m. no courting below 60 sulcl frous Hine ( 1903) late July & before 9:00 a.m. south side Yes !· through Aug of woods 1· thoraslcus 7 Haddow et 111. not stated nautical twllt3ht not stated 1 (1961) Uganda 'ttl sun ts 12 rain fore~ t below horizon !· tnslgnts_ 7 Harld'lw et al. not stated arri ves 25 mtn. not stated 1 (1361) Uganda later rain fol'est 1· phaneop1 Webb and lie 11 s not stated 8-9:00 p.m. not stated 1 (1924)

Hybomi tra aurl 1 i~s Bl ickle (1955) 6 July - JO July 9 a.m. - 5:00 p.~. 1-3 ft. No !!_. ctncta_ Balley (1948) 7 July - 29 July 8:30-9:40 11 .m. 1-4 ft. No 1;30-5:10 p.m. !!_. jllotus Philip (1931) 11 J uly - 12 July 9:30 a.m.- m~les perched No 12:00 noon on vegetation Chrysop\ fulgtnosa "'1cCreary ( 1940) 9 June - 10 June 9-10 a,m. mating pairs Yes resting on aqua tic vegetation !· re I nwe rdtf i Lavigne, Bloom 26 June - 4 Aug 7:27"' 11:02 a.~. coupl tng In air Yes and Neys ( 1968) fr(Jl1 3 tn. to 5 ft. high somet Imes accompanied by brief hover £. fulvaster Lavlgue, Bloom 13 June - 7 Aug 7:45"' 10:23 a.~. males coupled wHh Yes and NP.ys (1968) female in flight 7

Actual mating was observed for Jabanus americanus (= giganteus) by Hagmann et al. (1948). In this case "the male struck the female and connection was made in flight, after which the pair attached to a leaf, one holding firm there while the other hung motionless below." Evidence indicates that mating appears to be proceeded by hovering of the male, who is presently joined by a female, and the pair flies off to rest on the vegetation. Lavigne et al. (1968) present the most detailed account of the mating behavior of tabanid species, and for T. reinwardtii and C. fulvaster coupling aways occurred in mid-air. However, coupling was not always preceeded by hovering. Other Tabanidae are known which do not appear to hover before mate location and copulation. Mating pairs of Chrysops fuliginosa were observed by MacCreary (1940) to "rest upon cattails and other vegetation (in the breeding area). Upon being disturbed, they would fly erratically a few yards to another resting place without separating. " Hine (1903) observed a close association between ovipositing female C. moechus, males resting on vegetation, and mating. If hovering is actually a courtship behavior, undoubtedly vision is involved in detecting hovering time, location and possible mates. If hovering i s not involved i n courtship, vision may still be involved to detect the location, flight height (Roberts, 1975), flight velocities and other characteristics of the opposite sex. However, it is unreasonable to assume that vision alone is involved in the process of sexual recognition. 8

The statement that "Tabanidae can not sense sound" would be a very difficult one to defend . Never has an insect been shown not to have the capacity to react to vibrations caused by sound. The literature is replete with citations studying the various sensory structures of insects which have enabled them to tap certain frequencies of sound (Fletcher, 1978) (Ehrman, 1959) and utilize them for prey location (Cade, 1975), to escape from predators, in establishing territories, for mate location and in sexual isolation. Many families of flies have been shown to utilize sound. Evans (1966) and others have discussed the utilization of sound in courtship behavior for Culicidae, Chironomidae, Asilidae and Drosophi12.· Indirect evidence and speculation that Tabanidae utilize sound communication also exists. Philip (1931) was the first to suspect acoustics in species recognition when describing the activities of Tabanus (= Hybomitra) illota males. His lengthy quote will be given here because of the importance of the details observed: The males of T. illotus were also observed sitting about on grass and leaves exposed to the sun and generally over shallow standing water. They were seen to dart up as if chasing something and then return to the same or a neighboring leaf. Four males were seen for a time in about a 3 ft. square of space. (The next day) On arrival 5 T. illotus were noticed in the same location. The- five ... diminished to one about noon. They varied their position within this space but always returned to it following a quick dash after some indeterminate object. On returning, two or three would be closely following each other and would often alight on the first one to come to rest as if seeking copulation. They would irmnediately assume a still pose on their perch, the body slightly elevated 9

anteriorly, the abdomen usually touching the leaf behind, with the genitalia slightly protruding. In this pose, the front legs were usually doubled up underneath and not grasping the perch, but raised as if in a tactile or sensory position of some sort. Illl11ediately after alighting, they took a firm hold with the four posterior legs and rubbed the anterior legs together but never stroked the head as house flies do. At the approach of some interesting specimen, they ceased stroking the tarsi togther and lowered legs, elevating the knees in short jerks, acting as if trying to sense something before taking off after it. The object of their sorties could not be ascertained, the short dashes, when followed, seemed to be out and back for an unseen or for no particular object. Two or three times a female tabanid whirled around me and attracted a frenzy of attention on the part of the males flying up and away after the departing female but thier chase could only be followed with the eye momentarily. Once in a while an unidentified female would attract no notice, perhaps being of another species. One wonders if a tuning fork of the right pitch would cause simultaneous reactions. It was occasionally noticed that a male would drop his front legs and start crawling, at which time no notice was taken by it when the others darted off in pursuit of something (Philip. 1931). Other published material concerning sound produced by Tabanidae deals primarily with the fact that hovering males produce a distinctive whine (Evans, 1966; Nash and Ross, 1977; Mosier and Snyder, 1918), and that female r-oniops chrysocoma produce a characteristic buzz during ovi position and maternal behavior. In this case the "buzz" sound is produced "with the wings lifted up and forward, from which position they are rapidly vibrated, but not to such an extent as to touch the leaf" on which she has positi oned herself to guard the egg mass (McAtee, 1911; Schwardt, 1934). 10

Finally, field experience with horse and deer flies leads to more speculation. "Anyone having occasion to go near the woods is quickly aware (of Tabanidae) by the peculiar hum or rustle of their wings as they circle about the head. The insistent hum of the larger tabanids is readily distinguished, but the approach of a deerfly is frequently missed before it alights or begins feeding" (Philip, 1931). Collectors of tabanidae such as myself and Dr. L. L. Pechuman (personal communication) agree that one can often recognize species by the sounds produced by attacking females. This ability of collectors is indirect evidence that various species of Tabanidae produce unique sounds. METHODS AND MATERIALS

Collection Techniques Tabanid specimens were obtained by rearing adults from field collected late instar larvae and by field collecting adults. Larvae of Chrysops cincticornis, f. niger, f. callidus, and Tabanus reinwardtii were collected in May 1978 at Rockmill Dam Reservoir in Fairfield Co., Ohio. Specimens were reared in paper cups partially filled with the substrate in which they were collected. These cups were covered with perforated plastic cups with slightly larger rim diameters (Fig. 1). Rearing cups were stored at room temperature and were regularly watered, maintaining substrate.moisture. Carnivorous Tabanus larvae were placed individually in rearing cups, and Chrysops were reared in groups of up to five per cup. Adult Tabanidae were collected using either a modified Malaise Trap baited with dry ice and a shiny black sphere (Fig. 2) or an aerial net. The lack of collecting heads on the trap was essential for obtaining specimens in good condition (Drees et al., in press). During 1978, collections were made throughout Ohio and in West Virginia in order to obtain unusual or locally restricted species. However, in 1979, collections were made on a weekly basi s at Cedar Bog Nature Preserve, Champaign Co., Ohio, after obtaining a collecting

11 12 pennit from the Ohio Historical Society. Complete collection data for specimens recorded are presented in Appendix A. Specimen identifica tions were confinned by Dr. L. L. Pechuman, Cornell University. Specimens collected in the field were placed in plastic poultry bags and then stored in an ice chest at approximately 1s0 c. The low temperatures and lack of light in the cooler effectively immobilized specimens until recordings could be made. Recordings of wing stroke sounds were made in the evening hours (8:00 p.m. to 1:00 a.m.) on the day of capture. This recording schedule standardized the behavioral conditions of the flies and also pennitted specimens escaping from the holding chamber to be readily retrieved at the room light. Reared specimens were recorded as soon as possible after emergence, however, the exact time of eclosion could not be detennined.

sounds from the ground. An inner chamber was constructed of similar plywood, also with a hole for the microphone, and the space between the inner chamber and the inner surface of the cooler was filled with matted fiberglass ceiling tile. The inside surface of the inner chamber was also covered with ceiling tile. The top of the chamber was similarly constructed, although a rectangular hole was cut into it to house the felt covered specimen holder mount (Figs. 3 and 4). When the top of the recording chamber was attached to the outer plywood box with screws, the specimen holder mount fit snugly into the inner chamber, and the felt layer formed a sound barrier between the inner and outer plywood chambers. The mount enabled a specimen holder to slide easily in and out of the recording chamber. The specimen holder was constructed from 1/4 in. (6.35 mm) plexiglass and 1/8 in. (3.175 mm) diam. plexiglass rods (Fig. 4). A thermometer inserted in the specimen holder was secured with rubber stoppers. Four dead air spaces near the top of the holder formed a sound barrier while still permitting light to enter the chamber, facilitating the flight response of specimens being recorded. Specimens were attached to the tethering rod, and the height of this rod was adjusted so that the flies could rest on a plexiglass platform or trap door. By pressing on the rubber stopper attached to the top of one of the platform support rods, the trap door would lower away from the fly causing it to behave as if it were in flight. Releasing the rubber stopper resulted in the return of the platfonn to its original position because of a spring mechanism on the platform 14 support rod. As the specimen again made tarsal contact with the platform, flight activity terminated. The microphone installation was constructed from cardboard tubing covered with felt. A UHER M517 microphone was suspended in this tube, supported by rubber stoppers with holes drilled in them into which the microphone was inserted. The space remaining in the tube was filled with foam rubber to dampen sound. The microphone installation could be removed from the recording chamber for oral editing and corranentary, and then be reinserted to the proper depth for specimen recordings. The distance from the microphone to the specimen was one inch. Recordings were all made on Scotch 176-1200 URS magnetic tape using a UHER 4000 Report 5 portable tape recorder at a recording speed of 7-1/2 inches per second (ips) or 19 cm. per sec. (cps). The UHER 4000 has an audio range of 40-20,000 cps or Hz, a signal to noise ratio at 7-1/2 ips greater than or equal to 52 dB, and wow and flutter of+ 0.15%. Accurate tape speed was also verified by timing a reel of tape of known footage. The recording level was consistent for all but the larger tabanid species, including Tabanus sulcifrons, I· calens, I· nigrescens, and T. atratus. Recording times per specimen were generally between 15 and 30 seconds, although specimens displaying variations in sounds were recorded for longer periods and uncooperative specimen recordings were generally shorter in duration. The temperature, time of day, and date were recorded for each specimen taped. 15

2) Both wings were tapered or cut at a slight angle to the lon~ axis of the wing, narrowing the wing shape and reducing the chord. 3) One wing was cut in one of the manners described above. This method seldom resulted in both wings being of equal size or shape. After recording the sounds of the modified wings, the specimens were treated as described below, and the original wing lengths and areas were estimated by comparing the remaining wing size and shape to those of normal specimens. The area of the removed wings was calculated by substracting the area of the remaining wing from the estimated area of modified wings.

Temperature Modifications Although the recording temperature of each specimen was noted, the effect of tefT'4)erature changes on individuals was also examined. Eight specimens were recorded at ambient temperature and removed from the chamber. A hair dryer was then used to heat the chamber, and the specimen holder was reinserted. After the temperature stabilized, the flies were recorded again. This process could be repeated, noting the new temperature before each recording. 16

Unfortunately, this experiment could not be replicated because of the inability to cool the heated chamber.

Sona grams Tape recordings of Tabanidae were edited and deposited in the Borror Laboratory of Bioacoustics in the Department of Biological Sciences, The Ohio State University. Specimen recordings were replayed on a Technics 1500 (Panasonic) tape recorder through a Scott 44A integrated amplifier into a Kay model 7029A Sona-Graph. Each specimen recording of acceptable quality was graphed on Kay Elementrics Cooperation type B/65 sonagraph paper, with the following settings: frequency range 10-1000 Hz, gain equal, calibration at every 50 cycles, narrow band, mark level and AGC on 4, and with a linear scale. All of the variations of sounds produced by a specimen were depicted, while only four or five seconds of steadily 11 flying 11 specimens were graphed. The entire recording and graphing technique was calibrated using a tuning fork of the musical note 11 A" at 440 cycles per second {cps) (Fig. 8). Each sonagram was also marked with a frequency calibration mechanism which produces horizontal marks on the graph at every 50 cps. These calibration marks were used to produce a ruler with 10 cps increments (Fig. 10). This device was utilized to measure the frequency bands of the sounds present in the specimen recordings. Both the maximum and minimum wing beat rates in each sonagram were measured in order to determine the frequency ranges for each species. For species comparisons, however, only the maximum wing beat 17 rates were utilized. The fundamental tone or wing beat rate was calculated for each specimen by averaging the differences between all of the frequency bands (fundamental+ harmonic overtones). This method was used to overcome possible inaccuracies in the measuring device.

Anatomical Measurements Wet Weight: Directly after the specimens were recorded, they were freeze killed in the plastic poultry bags. Each fly was then weighed on a Mettler Type H16 Balance to the nearest 10-4 g in order to determine the wet weight or body mass. Flies were weighed individually to prevent thawing, and then they were placed quickly in 2 dram

(17 x 60 mm) Kimble Shell Vials and sealed in with Parafilm 11 M" Laborotory Film. Vials were stored at -1a0c in a Sears Coldspot Frostless refrigerator-freezer. Some specimens were pinned and mounted rather than being frozen. 18

Wing Slides: Wing length, chord, area and aerodynamic center of many specimens were calculated from slide-mounted wings which had been removed from frozen or pinned specimens. Wings were placed in a drop of acetone on No. 3010 pre-cleaned Gold Seal micro slides and covered with Esco 22 x 40 nm, No. 1 thickness microscope cover glasses. Cover glasses were attached to the microscope slides with 7/32 in. (5.56 mm) wide Scotch splicing tape. In this manner, many wings of one species could be mounted together on a single slide. Wing slides were then projected with a Bausch and Lomb VH Micro-Projector calibrated with a B&L micrometer so that 0.1 mm of the mounted wings equaled 1/16 in. {1.5875 rrm) on the wing drawings (a magnification of 15.9 times). All wing measurements were made from the resulting wing drawings.

Chord: The width of the wing, or chord, will vary along the length of the wing. The chord line, drawn perpendicular to the wing span line, will be longest at a point along the wing span line referred to as chordmax The point at which chordmax occurs is measured at a set distance along the wing span line. In this study, chord lengths were measured at approximately 25 and 55% of the span line as measured from the base of the wing. 19

Wing Area: The area of each wing was calculated by weight. All of the wing drawings were Xerox reduced to 62.5% of their original size. Each wing was then cut out to be weighed. To simplify the cutting procedure and to insure consistency, the wing bases were truncated by cutting along a line extending from the humeral cross-vein to the basal-most point of the axillary cell. The weight of each wing was then divided by 1/4 of the weight of a 25/32 x 25/32 in. (19.84 x 19.84 mm or 2 cm2) piece of Xerox paper, or rather the weight of 1 mm 2 of wing surface.

Effective Aerodynamic Center: The lift required by Tabanidae in order to fly is generated primarily by flapping. Lift produced by forward speed or gliding is negligible (Appendix B). The effective aerodynamic center, EAC, is calculated by first determining the effective aerodynamic center of the span, (EAC)s, and then the effective aerodynamic center of the chord, (EAC)c. Combined, (EAC)s and (EAC)c define a point on the wing at which the mean aerodynamic forces acting on that flapping wing occurs. 20

The effective aerodynamic center of the span takes into account that the wing tip velocity is higher than that of the wing base, that the chord length changes along the wing span line, and it assumes that the angle of attack along the wing span line is constant. As a result, the effective aerodynamic center, EAC, is dependent upon the shape of the wing: a wing with a narrow tip and a wide base will have a more basal EAC than a wing with a rounder tip and a narrower base. The effective aerodynamic center of the span (EAC)s, is calculated by first dividing the wing into a number of equal segments along the wing span line, which has a length, L, representing the total wing length (Fig. 5). The number of segments is n, and i is the segment number as countedfromthe wing base. In the middle of each segment, the chord length, Ci, is measured. Now the width of each segment is L/n, and the area of each segment is L/n·C;. The aerodynamic force on each segment is equivalent to : L·l/n·C.·W 2·(i-l/2)2 l max where Wmax is the flapping velocity of the wing tip. The aerodynamic moment at the base of the flapping wing is: L·l/n·C. ·W 2.(i-1/2)3 l max and, the total aerodynamic moment for the wing is obtained by summing the aerodynamic moments of all of the segments:

n 3 2 E{L·l/n·(i-1/2) ·C.·W } i l max 21

The effective aerodynamic center of the span, (EAC)s' is then calculated by dividing the total aerodynamic moment by the summation of the aerodynamic forces on each segment and dividing this value by the wing length, L, as follows: n 3 E{(i-1/2) ·C.} ,. 1 n ~{(i-l/2) 2 ·Ci} 1 The product, multiplied by 100, is the percent of the wing length from the base of the wing at which (EAC)s occurs. The effective aerodynamic center of the chord, (EAC) , is c calculated in a similar manner when it is assumed that the local aerodynamic center of each segment is at 1/4 chordlength from the leading edge or costal margin. This is in accordance with classical aerodynamics. The difference between the segmental EAC (the inter section of C. and the wing span line) to costal margin distance, a . 1 l (Fig. 5), and 1/4 Ci is calculated for each segment. Then the aerodynamic moment is calculated about the wing span line and divided by the summation of the aerodynamic forces on each segment. and the result is divided by the wing length, L:

n ,~ {(i-l/2) 2 ·c; ·(ai-l/4Ci)} (EAC ) c - [ 1 2 ~{(i-l/2). ·C.}, l 22

The product of this equation, multiplied by 100, is a percent of the wing length which represents the distance in front of (if (EAC ) i s c positive) or behind (i f (EAC)c is negative) the wing span l ine where the effective aerodynamic center of the chord lies . For a sample calculation the effective aerodynamic center, see Appendix C. RESULTS ANO DISCUSSION

Elements of Tabanid Flight Sound Tethered flies, upon losing tarsal contact with the trap door, began actively flapping their wings. Their legs folded and were held in an attitude to the body (Figs. 6 & 7) typical of normal flight (Nachtigall, 1968). For this reason and for the sake of brevity, the sounds of the flapping wings produced by the tethered flies will subsequently be referred to as flight sounds. Tabanid flight sounds are produced by the flapping of the wings through the wing stroke cycle. The complex movements of the wings through this cycle have been described for Callipho~~ by Nachtigall (1968) and were not examined further for Tabanidae. However, the assumption is made that the wing stroke cycle in Tabanidae is similar to that of other Diptera. As a result of the thoracic click mechanism (Prinqle, 1957), both wings beat synchronously at all times. The halteres, the only other actively moving structure on the thorax, "vibrate with the same frequency as the fore wings but in antiphase" (Chapman, 1971). Due to their small size, their movement produces no significant noise. The net result of the wing movements is the displacement of air to Produce the thrust and lift required for flight. As a by-product, sound is produced with a frequency equal to the rate at which the ,

23 24 wings beat. Hence, the wing beat rate is often referred to as the wing beat frequency. The frequency of the wing beat rate is also called the fundamental tone. A total of 420 tabanid specimens, representing 39 species in 6 genera, was recorded, sonagraphed, and measured. Figures 11 and 12 depict the mean maximum wing stroke rates and standard deviations measured in cycles per second (cps) for the 39 pangoniine and tabanine species recorded. Species are listed for each subfamily in the order of decreasing wing beat rates recorded for all temperature levels and throughout the two collecting seasons. The range limits for specimens recorded were 91 cps for a female Tabanus atratus to 193 cps for a male I· guinguevittatus. Unlike the type of sound wave produced by a tuning fork (Fig. 8), the sounds produced from dipteran flight are produced in pulses. These pulses result from the thoracic click mechanism in which the upstroke is much faster and louder than the down stroke (Bennet-Clark and Ewing, 1968). As a result of the pulse type wave, harmonic overtones are produced with frequency levels at multiples of the fundamental tone (Fig. 9) (Webb et al., 1975). The intensity of these overtones decrease and decay as their frequency levels increase. The number of hannonics seen in any particular sonagraph results from the loudness of the actual wing stroke noise, the distance of the specimen to the microphone andthe input and output level settings of the recording and playback equipment. Nevertheless, the intervals between the hannonic overtones are predictable from the fundamental tone (Fig. 9). 25 Other non-harmonic overtones occasionally appear in sonagrams.

These include frequency levels at ~ the distance between harmonic intervals (Fig. 13) and occassionally at 1/3 the distance. Although not artifacts, these overtones do not occur consistently within any species. No explanation for their occurrence has been attempted. Possible sources for artifact sounds with the recording technique employed were 1) wings hitting the tethering rod, 2) torn wings, and 3) resonance of the tethering or platform support rods produced by the specimen being recorded. The latter case occurred occasionally with larger specimens, but the problem was corrected by dampening these rods. These problems were usually audible at the time of recording and were corrected or the recordings were discarded.

Temperature and Sound The influence of temperature on the rate of movement and sound production for cold blooded animals such as insects has been well documented in the literature. Although Greenewalt (1962) did not consider this factor, Costello (1974) has discussed the effect of temperature on the wing beat frequency of mosquitoes. During this study, specimens were recorded at ambient temperatures ranging from 22 to 33°c. This range was divided into 3 groups, 101 specimens were recorded at a temperature less than 26°c. 229 specimens between 26 and 2a0 c, and 89 specimens above 2a0 c. Of the 30 species recorded at more than one temperature range, only 14 had higher average frequencies at higher temperatures (a positive response). 26

In other words, less than ~of the species had faster mean wing beat rates at higher temperatures. Furthermore, the degree of positive or negative response among species was inconsistent. These results indicate that the extent of variation of sound produced among individuals is too great and overcomes the more subtle changes in frequency induced by temperature changes. A more direct approach is to study the effects of temperature on individuals. Each of the seven tabanid specimens recorded at two or more progressively higher temperatures (range 22 to 35°c) displayed a positive linear response (Fig. 14, line 3). The average positive response was an increase of 3.4 cps per degree (SD= 1.6). This figure is less than the 6.3 to 6.7 cps/1°c reported for Aedes aegypti females by Costello (1974). One specimen, a female Chrysops beameri recorded at 26, 27, 30, and 33°c (Fig. 14) displayed positive responses between the 26 and 27°c, and between the 30 and 33°c recordings. However, between the 27 and 30°c recordings the specimen decreased its wing beat rate 16 cps (fran 148 to 132 Hz). Although such a decrease may not have been as pronounced if the specimen had actually been in continuous flight. the observation has significance because it illustrates clearly the behavioral component of wing beat rate control. Costello (1974) argues that temperature induced changes in wing beat rates are associated with physical processes of the muscle tissues, the exoskeleton and resilin components rather than thermochemical reactions of the indirect flight muscles. However, as Pringle (1957), 27 mentions, "the extent of the departure from harmonic motion (the amount of click action) is fully under the control of certain accessory indirect muscles the pleurosternals of Diptera". Although behavioral control of flight speed may not be as noticeable in mosquitoes, different sounds produced by individual Tabanidae are often noticeable even under field conditions. Moreover, it is this capacity for behaviorally modifying the wing beat rate that results in the amount of variation of wing beat frequencies recorded among the individuals of tabanid species, obscuring the effects of temperature on a group of specimens. The decreased effect of temperature changes on the tabanid vs. culicid wing beat rates could lead one to speculate that ambient temperature changes have less effect on insects with greater body or muscle masses . Although Hocking (1953) reported the inability to initiate flight in Taban~ affinus below so°F (10°c) myogenic heat is produced once flight activity begins. Many authors (Gaul. 1951) have found the temperature of the wing muscles during flight may be much higher than the ambient temperature. Some flying insects have thus been claimed to be heterothermic, or animals which "can produce enough heat to sustain an elevated body temperature but that become essentially ectothermic when they are inactive or dormant" (Heinrich and Bartholomew. 1972). The absence of significant differences among individuals of different species recorded at various ambient temperatures tends to support this assumption. Small animals have comparatively more surface area to volume than larger bodied species 28 and therefore lose heat more rapidly to their environment. However, no quantitative relationship can be established from the data available because 1) the amount of tracheation to surface area of a mosquito or tabanid thoraces is not known, and 2) Heinrich and Bartholomew (1972) found that the thoracic temperature of a tethered insect is less than that of an insect in free flight. For the sake of consistency and to ensure that the effect of temperature was negligible, however, only those specimens recorded in the temperature range of 26 to 2a0 c were utilized to compare differences among species. Specific means recorded in this range tended to cluster more tightly due to the high number of samples and possibly the effect of a small temperature range (Fig. 15).

The Effect of Wing Dimensions, Wet Weight and Wing Loading on Flight Sound The effects of physical dimensions on sound production were investigated during this study. Possible physiological influences of age and energy available for flight were not considered, but will be discussed in a later section along with the possible effects of behavioral factors. Environmental factors including temperature and tirre of day have been controlled. Table 2 lists the results of the physical parameters measured: wing length. wing area, wet weight, and wing loading. The wing beat frequencies of specimens recorded at 26 and 2s0 c have also been provided. TABLE 2. Means, standard deviations, and sample sizes for wing lengths, wing areas, wet weights, wing loads and wing beat frequencies (26-2C0 c> for thirty-nine species of Tabanidae. 2 SPECIES WING l..ENG1li (mn) WING ARF.A (11111 ) WET WEIGfT (mg) WING UlADING (mgj111n2) WING BEAT FRF.QUfNCY (cps) 26-280C Pangoniinae:

1. Stone~1a tranqu1lla 10 .13t 0 . 25 ( 3) 23.8lt L03 (2) 39. lO:t 3. 30 (3) 0.80t 0. 11 (2)

2. Chrysops beamer1 7.llt 0.37(14) 13.37t 1.27(12) 9.30.t: 2.30(12) 0.32t 0.06(10) 143.32:t S.90 (5)

3. Chrysops brunneus 8.13:t 0.61 (3) 15.95t 2. 62 (3)

4. Chrysops callidus 7.65* 0.35(17) 14.41* 1.94(14) 19.40:t 5.00 (5) O.S9:t 0.10 (3) 157.46t 7.30(13)

s. Chrysops cincticornis 7.67J:. 0 .61(12) 14 . 30t 2.47(13) 139.09.tl2.70 (6)

6. Chrysops cuclux 8.00t 0.42 (2) 14. 7 3t 1. 42 (2) 137.13t 5.83 (2)

7. Chrysops flavidus 8.25t 0.21 (2) 17.93t 1. 23 (2) 12.30 Cl) o. 36 (1)

8. Chcysops ge.rninatus 6.04t 0.49(16) 9. 72* 1.35(13) 6. 75* 3.40(13) 0.33:t 0.07 (7) 153.27.t 9.43(11)

9 . Chcysops impunctus 6.68t 0.21 ( 5) 11.31.t 0.69 ( 4) 8. 70.t 2. 40 ( 4) 0.36t 0.09 (3) 148.65• 0 .21 (2)

10. Chrysops indus 8.27t 0.23 (3) 17.60t 0 . 90 (3) 16 . 80 (1) 0.541 (1) 135. 00 (1)

11. Chrysops ntaC']uart1 7. lOt 0. 31(19) 13.38t 1. 47 (17) 8. 20t 1. 80 ( B) 0.30t 0.08 (6) 136.85•12.04(13)

12. Chcysops moechus 8.0 (1) 17.99 (1) ------13. Chcysops niger 6. 93+ 0.25 (3) 12.07* 1.10 (3) 9. 5 (1) 0.39 (l) 142 .50.t 3.54 (2)

14. Chcysops pikei 7.04~ 0.32 (8) 12.48t 1.27 (7) 9.lOt 0.70 (5) 0. 37-t: 0.62 (4) 141. 20-t: 7.95 (5)

15. Chcysops shermani 8.20 (1) 16. 57 (1) ------132.00 (1)

16. Chrysops uni vittatus 6.S3t 0.39(19) 10.40+ 1.37(19) 10.42* 3.50 (9) 0.44t 0.12 (8) 145.50* 5.90 (6)

17. Chrysops vittatus 7.87+ 0. 44(28) 15.56+ 1.84(25) 11 . 2St 3.45(11) 0.39t 0.10 (6) 129.69tl0.81(23)

Tabaninac

18. Haematopota rara 7.40+ 0.23 (5) 13.16+ 1.13 (5) 9.80+ 0.70 (7.) 0.36+ 0.06 (3) 2 2 SPECIES WING Lf:NGrn (llVll) WING ARFA (llVll ) WET WEIClfl' (mg) WING LOADING (mg/mn ) WING BFAT F~UENCY (cps) 26-28°c

19. Atylotus bicolor 8.50• 0.56 (5) 17.09* 2.61 (5) 25.70± 7.50 (4) 0.79:t 0.21 (4) 174.72± 9.73 (5)

20. Atylotus ohioensis 7.10• 0.43 (8) 12.0lt 1.50 (8) 13.95t 9.26 (8) 0.43t 0.09 (8) 158.67:t 9.62 (6) 21. Hybomitra di££icilis 12.37t 0.40 (3) 32.46:t: 0.55 (2) ------119.50± 9.69 (4) n.. Hybomitra pechumani 9.50 (I) 20.16 (1) 45.30 (1) 1.12 (1) 149.17 (1)

23. Hybomitra lasiophthalma 11.01* 0.59(14) 26.17± 2. 78(10) 42.90± 9.93 (6) 0.78:t 0.13 (4) 137.92* 8.25 (2) 24. ll.90:t. 0.66 (3) 32.02± 4.97 (3) 119.43t 2.23 (2) Hybomitra microcephala ------~------25. Hybomi tra rniniscula 8. Ti.± 0.53(26) 17.26:1:. 2.28(25) 21.96t 6.94(17) 0.68-t 0.09(16) 135.19tl7.33(20)

26. Hybomitra sodalis 11.60:1:. 0.61 ( 4) 31.22:t:2.76 (4) 76.SOtlS.79 (5) l.08:t: 0.04 l3) 137.04:tll.30 (3) 27. Tabanus atratus 23.10 (1) 123.4 (l) 397.0 (1) 1. 59 (1) ------28. Tanabus calens 20. 75* 1.63 (2) 95.93*17.56 (2) ------102.80 (1) 29. Tabanus nigrescens 19.13* 0.12 (3) 82. 73t. 6.75 (3) 329.2.:t13.SO (3) 2.00:t. 0.19 (3) 115.00±14.43 (3)

30. Tabanus nigripes 9.65• 0.43(28) 21. 63± 2. 32 (24) 39.80±10. 78(26) 0.91± 2.32(24) 139.35:t:23.36(20)

31. Tabanus pumi 1 us 7.28:t: 0.35(16) 12.88:t: 1.28(15) 19.60± 8.16(13) o. 77± 0.26(13) 154.15:t:l0.16 (8)

32. Tabanus quinquevittatus 9.29* 0.42(23) 21. 86:t: 2.05(19) 41. 66:t 6. 99 (17) 0.96:t 0.07(15) 148.73±16.28(16)

33. Tabanus reinwardtil 13. 53:t. 1.07 (3) 43.81± 7.32 (3) 117.0 (1) 1.13± (1) 125.00 (1)

34. Tabanus sackeni 12.12* 0.53 (6) 33.65:t 2. 77 (5) 67.28± 0.02 (6) 0.92:t:: 0.10 (5) 123.40±10.47 (2)

35. Ta ban us simi lis 10. 34* 0.45 (7) 2S.22:t: 1.90 (7) 44. 70-tll. 58 (7) 0.82* 0.10 (7) 137.25:tl6.80 (5)

36. Tabanus sparus millerl 7. 58-t: 0. 32 1 7) 13.99:t: 1.38(17) 21.06:t: 7,50(16) o. 79* 0.14(16) 163.60± 9.93(12)

37. Tabanus sulcifrons 17.SOt 1.15(14) 72.57t 4.12 (9) 217.96:t25. 72(12) 1. 56* 0. 09 (7) 121.62t 7.21(10)

38. Tabanus superjumentariusl4.l9:t 0.58(17) 47.18.t 4.03(16) 122.18 ±18. 00 (11) 1.32* 0.12(10) 118. 96:1: 6. 45 (8)

39. Tabanus trimaculata 13. 19t 0. 71 (IS) 40.22-t 4.88(11) 123.QO-t29. 60 (10) 1. 52± 0.41 (8) 127.61±13.09 (8)

40. Tabanus vivax 10.10 (1) 23.54 (1) 38.60 (1) 0.82 (1) w ------0 31

Wing Length: Wing length (a wing dimension) and wet weight were both found to be correlated with wing beat frequency. A high negative correlation, significant to an alpha level of 0.01, was found for the effect of wing length (X) on the wing beat frequency (Y) for both Chrysops and Tabaninae. The regression line for 103 specimens of Tabaninae (Fig. 16) was found to have a slope of -0.32, and data points cluster around a line described by the following equation:

0 316 v = 288.712 x- · The line fitted to the data from 40 Chrysops specimens (Fig. 16) has a slightly steeper negative slope of -0.46, described by the following equation: 0 464 v = 344.782 x- · Plotted on a log-log scale, these lines are straight with ranges of 4.8 to 8.9 mm for Chrysops, and 6.3 to 23.1 mm for Tabaninae. Numbered points in Figure 16 refer to the mean values of species listed in Table 2. These results were plotted along with the regression line for 13 species of Canadian mosquitoes recorded at 2J0 c (Belton and Costello, 1979) and Greenewalt's boundary line (Greenewalt, 1962) in Figure 17. Greenewalt's boundary line is apparently the upper statistical limit of wing beat rate and wing length calculated from all insects for which this type of data occurs in the literature. Interestingly, the largest tabanids approach but do not exceed this limit. 32

Chord: Another parameter of the wing, the average maximum chord per species, occurs at approximately 25% or 55% of the wing length from the tegulum. A linear relationship was found between wing length and maximum chord such that for every 1 nm increase in the length of the wing, the chordmax will increase by 0.34 nm (correlation coefficient= 0.99). Thus, chord length is related to wing beat frequency in the same manner as i s wing 1eng th. During the measurement of these chord lengths, some tabanid species were noticed to have the average maximum chord at 55%, while other species• average maximum chord occurred at 25%. This either-or situation occurred because of the indentation along the posterior margin of the wing at the point where the Cu 2 + 2A wing vein (Comstock-Needham system) and the posterior wing margin join. Generally, the larger tabanid species were found to possess more tapered wings with the chordmax at 25%. These results have indicated the existence of consistent and distinct differences in the wing shapes among tabanid species even among species with similar average wing lengths.

Wing Area: In order to find a wing parameter which might have a higher correlation to wing beat frequency, the wing area of each specimen recorded (for which wings were available) was calculated. Values for wing area encompass both the values of wing length and chord, and thus are related to wing shape. Again, the correlation coefficients were significant to the alpha level of 0.01. However, neither the 33 correlation coefficient for Pangoniinae (rn = 70 = -0.372) nor Tabaninae (rn = 118 = -0.666) was more significant than those for wing length and wing beat frequency (rn = 40 = -0.551 and rn = 103 = -0.701, respectively). The relationship between wing beat frequencies (Y) and winq area (X) for the two subfamilies was described by the following equations: Pangoniinae: Y = 217.303 x-O.l6288 Tabaninae: Y = 246.01789 X-O.l 7931 The difference between the slopes of these two equations (-0.16288 and -0.17931) is very small. A non-dimensional shape factor was calculated for tabanid wings by dividing the square root of the area of a single wing by the wing length (/rnrn 2/rnm). For the 335 individuals measured, a regression line, significant to a= 0.01 (r = -0.46585), for the relationship of wing length (X) to this shape factor (Y) is described by the following equation:

v = o.56131 x-0 ·6168 The mean shape factors for 40 species measured have been plotted together with mean wing lengths and appear in Figure 18 along with the regression line calculated for individual specimens.

Effective Aerodynamic Center: In order to investigate possible aerodynamic differences of tabanid wings which could result from different shapes, the effective aerodynamic center was calculated for a few of the wings which represented extremes in wing shape variation. The effective aerodynamic centers (EAC) of the span and chord of the 34 wings of the following species were calculated:

Species (EAC) (EAC)s c

Chrysops bruneus ~ 70.8% 2.8%

Chrysops bruneus ~ 70.7% 2.2%

Chrysops bruneus ~ 71.1%

Chrysops cin~ticornis ~ 68.9% Chrysops cincticornis c! 69.1%

Chrysops geminatus ~ 70.9%

Chrysops moechus ~ 69.3%

Haematoapota rara ~ 70.5%

Haematoapota rarA_ ~ 70. 3%

Hybomitra difficilis ~ 69.3%

Tabanus nigr!~ens ~ 69.0%

Ta ban us ni 9_!:_~ pes ~ 70.1%

Tabanus quinsuevittatus ~ 70. 5~: x = 70.0%

Results indicate small. but consistent differences amon9 species. As predicted, the more tapered the wing. the more basal the (EAC)s and the closer the (EAC) to the wing span line. However, the minor c differences in the EAC of these species indicate that the methods by which Tabanidae achieve flight aerodynamically are very similar, and that wing shapes will at best have minor or secondary influence on wing beat frequency. 35

Wet Weight: The wet weight of specimens was measured for 241 of the specimens recorded. Because of the collecting methods employed, the assumption was made that a11 specimens were unfed or partially fed and were in pursuit of a bloodmeal (Duke et al., 1956). Even with this assLftllption, the average standard deviation from the mean wet weight (90.7%) was about 1.5 times greater than the standard deviation from the mean wing length (59.9%). In other words, wing length is a more consistent parameter. This variation in wet weight can be due to the fact that Tabanidae, besides feeding on blood needed for ovariole development, will imbibe fluids such as nectar in order to maintain energy required for flight. Nevertheless, the correlation between wet weight and wing beat frequency was still significant to the alpha level of 0.01, at least for Tabaninae (rn = 103 = ~0.650), but less significant than the correlation between wing length (Y) and wing beat frequency (X). The equation for the regression line is Y = 199.439 x-0·9499 . The correlation for Chyrsops was not significant. Measurements of weight and wing length by Hocking (1953) of unfed females of Tabanus affinus, I· septentrionalis, Chrysops furcata and f.. nigripes agree closely to those for similar sized tabanids in this study. Greenewalt (1962) has determined regression lines for the relationship of wing length (X) and wet weight (Y). His figures show two regression lines, one for birds and one for insects: 36

0 3449 Birds: X = 0.0079 v2· 899 or Y = 5.3101 x · 0 3376 Insects: X = 0.677 v2·9617 or Y = 2.4817 x · Regression lines for Pangoniinae and Tabanidae recorded during this study are shown in Figure 19. The equations for these lines are as follows: Pangoniinae: X = 0.00317 v4· 1105 or Y = 4.0538 x0· 2433 2 9863 0 3350 Tabaninae: X = 0.00419 v · or Y = 2.8433 x · (Note that Greenewalt has given the equation for the relationship between body weight vs wing length, but his slopes indicate the relationship between wing length vs. body weight. Thus, Greenewalt's equations are given first, followed by equations describing lines A, B, C, and D in Figure 19 . ) Except for Pangoniinae. all of these lines have a slope of 3. Interestingly, all of the data points for Tabanidae measured during this study fall above Greenewalt's line for insects, as do Hocking's (1953) data points for unfed female Tabanidae. However, after feeding on a sugar solution, the weight of Hocking's Tabanidae fell slightly below Greenewalt's regression line. The effect of a blood meal on body weight is even more dramatic. Gooding (1972) has summarized methods for measuring bloodmeal sizes for haematophagous insects, and has compiled estimates for Hyb~mitr~ frontalis (Walker) (=I· sep~entrj_Q_~ali~) and~- ~ffinis (Kirby) by

Miller (1951), and for I_~,?nus guinguevittatus ~Jiedemann and I_. sulc_j_~ro~ Macquart by Tashiro and Schwardt (1949). Values indicate an average increase of about 217% the weight of unfed females after feeding to repletion on blood. This increased weight would shift the 37 regression line in Figure 19 calculated for unfed Tabaninae to the right, to the other side of Greenewalt's regression line for insects (D). Added body weight could effect the wing beat rate if the angle of attack of the wings during the wing stroke cycle does not change.

Wing Loading: One method of discussing the effect of body weight aerodynamically, is to express the relationship between wing area and wet weight in terms of wing loading: body mass/area of both wings. As values of wing loading increase, either the weight of the body is increasing relative to the wing area, or the wing area is decreasing relative to the body weight. Among tabanid species, there is tendency for wing load values (Y) to increase with increasing size or wing length (X) (rn = 204 = 0.79121) such that: v = o.0345 x1· 3733 Theoretically, as wing loading increases, the power needed for flight should also increase. Increased power can be achieved by Diptera in two ways: 1) by increasing the wing beat rate and 2) by increasing the angle of attack during the wing stroke cycle. Although wing loading increases with size, there is a negative correlation between wing loading (X) and wing beat frequency (Y), at

least for the mean values measured for tabanine species (rn = 16 = -0.7349), such that the equation for the regression line is:

v = 135.851 x- 0 · 2108 These conflicting phenomena, plus the structural aspect of tabanid wings, play an important role in establishing the upper limits of 38 tabanid size relative to the capacity to fly. "In similar figures the surface increases as the square and the volume (V) as the cube, of the linear dimensions (L) 11 (Thompson, 1952). Likewise, in Tabanidae the wet weight (Y) increases proportionally to the square of the wing area

( x): v = 0.0175 x2 (Greenewalt's formula for the relationship between wing area and body weight had a slope of 1.5 rather than 2.0.) As scale increases then, there will be a point at which the lift generated by wings of a certain area will be overcome by the more rapidly increasing volume or mass of the body. Of course, the mass of the female tabanid must also include the weight of the blood meal. The discussion above has attempted to describe the effect of scale on wing beat frequency and wet weight among tabanid species. However, the effects of wing loading are most clearly evident when comparing species or groups of species of similar size. Three species of Chrysops and two tabanine species all have an average wing length of 7.2 mm (Chyrsops beameri, f. pikej_, C. callidus, Atylotus bicolor, and Tabanus pumilus). The regression lines for wing beat rate vs. wing length indicate that Tabaninae have higher beat rates than Pangoninae of equal size (Fig. 16). The difference between the two groups was found by comparing means for wing loading of 17 Chrysops specimens and 21 tabanine specimens using the Student Newman-Keuls test. Results indicate a difference in wing loading between the two groups significant to the alpha level of 0.01. This difference in wing loading for unfed 39 females of the two subfamilies, resulting from the increased body mass (perhaps muscle mass) in Tabaninae, provides an adequate explanation for the observed differences in wing beat rate. Among the members of a single species, the effects of wing loading on wing beat rate are obscured. No significant correlation was found for either the effect of wing length, or wing loading with the wing beat rate. Apparently, the technique of tethering specimens for recording has led the flies, free from the effects of gravity or drag, to display their full range of flight behavior in an attempt to escape.

(Many specimens, of course, beat their wings or 11 flew" very steadily while tethered.) Sotavalta (1947) has discussed the effects of tethering insects in a fixed position for a number of insect groups and has found that Diptera, "which possesses the greatest relative elevating power (up to 200% of the body weight excessive)" of all insects, were among the most active when tethered. His findings agree with Chadwick

11 (1939) that "a fixed insect is an insect with a full load • Apparently, individual specimens of one species have the capacity to achieve both the maximum and minimum wing beat rates possible with their morphological and physiological characteristics, whether or not they have just fed on a blood meal (energy for flight is supplemented by the intake of carbohydrates). Similarly, there is no reason to assume that unfed flies will always fly with lower wing beat rates. Again, flies can achieve the power needed for flight by balancing the effects of the wing beat rate and the angle of attack during the wing stroke cycle. Thus, an unfed fly can beat its wings at a high rate 40 while "feathering" or decreasing the angle of attack during the wing beat cycle to achieve a relatively low forward speed. Wings of 17 tabanid specimens (6 species) were modified by either truncation or tapering. The wing beat rates of 95% of the specimens increased after modification. These results agree with those of Sotavalta (1947). However, no significant correlation was found between the amount of wing area removed and increased wing beat rate, because of the small sample size. Decreased wing area changes wing loading, but the reason the wing beat rate increases is due to the change in the resonant mechanical frequency (rmf) of the wing. Accordinq to Hocking (1953), "It seems clear that both the wing muscle system and the haltere and the muscle system in Diptera vibrate at their own resonant mechanical frequency. Were this not so, the energy loss from the repeated changes in the direction of the wing movement would surely be impossibly high. This frequency depends only on the moment of inertia of the system, and the dimensions and elastic moduli of the terga and flight mus cl es, but may be modified by air damping." Though it would be a difficult task to calculate the rmf of the dipteran wing system, the implications of the existence of such a frequency are applicable to the sounds of Tabanidae: as an object increases in size, the rmf becomes lower (for example, the strings on a violin vs. the strings on a bass). Thus, larger Diptera have lower wing beat rates than smaller Diptera. Furthermore, when flies beat their wings at a rate different than that of the rmf, more power is consumed and there exists the possibility that the elements of the sound produced by the movement of the wings will interact with the 41 elements of the wings' rmf. In fact, this is the most likely explanation for the variations in the intensities of the fundamental and harmonic overtones observed in the sonagrams during this study and those described by Belton and Costello (1974).

Loudness or Sound Intensity The previous section discussed the implications of the resonant mechanical frequency of the wing structure, determined by the shape and size of the wing, and the elastic properties of the thoracic box. The latter results from structural composition of the thorax plus the modifying effect of the pleuro-sternal muscles as described for Tabanidae by Bonhag (1949) and as discussed for Diptera by Pringle (1957). The interaction between the rmf and the elements of the sound waves produced by the wing stroke results in interference or reinforcement of the fundamental tone and overtones of flight sounds. This capability of flying insects to increase the volume (loudness) of certain components of the sound produced may be of interest in a biological sense. Male mosquitoes have been shown to react most strongly to the fundamental frequency of the flying female (Roth, 1948). Nevertheless, the possibility that insects could detect overtones resulting from the wing beat rate cannot be ruled out. Because all but the larger tabanid species were recorded at a constant recording level, and the microphone to specimen distance was also fixed, the loudness or intensity of the flight sounds among species could be compared. Loudness was estimated from a VU meter, 42 although this procedure is crude. Individual specimens are capable of modifying the loudness in two ways. 1) The intensity is directly proportional to the square of the frequency of vibration, an increase in wing beat frequency will result in greater intensity. This phenomenon is seen in sonagraphs. As the fundamental tone produced by a specimen increases, the number of harmonic overtones increases. 2) Intensity is also directly proportional to the square of the amplitude of the sound wave or rather to the displacement of air. Thus, a specimen can increase its intensity by increasing the angle of attack of the wings during the wing stroke cycle. without changing the wing beat rate. This phenomenon is also evident in the sonagrams of specimens recorded. Since intensity is related to air displacement, specimens with larger wing areas will obviously be louder. This phenomenon is evident from the VU readings and the average estimated intensities of the species recorded and measured , plotted against wing area.

Sexual Differences of Tabanid Sound As discussed in the introduction, only male Tabanidae are observed to hover in a stationary position. Females of certain species (i.e. Tabanu~ sackeni) will fly extremely slowly, however, they never actually remain stationary in the air. Hovering is the most power-demanding type of flight since no lift is derived from the forward motion. 43

Very few males were collected and recorded during this study. Of the eight males recorded (1 Chrysops cincticornis, 4 !il_bomitra miniscula, 1 Atylotus bicolor, and 2 Tabanus quinquevittatus) all but two specimens had higher wing beat frequencies than the average corresponding female wing beat frequencies. Due to the small sample size. however, these differences were not statistically significant. During actual hovering behavior in nature, the wing beat rates are likely to be much more constant and higher in pitch than those recorded for males tethered to a stationary rod. Recordings of hovering behavior are highly desirable and two unsuccessful attempts were made to locate and record hovering male !i.Zt>Omitra miniscula at Cranesville

Swamp , Preston Co., ~Jest Virginia during August of 1978 and 1979, where they had been observed to be abundant in August 1976. The lack of success during these trips was due to poor meteorological conditions cool, cloudy weather. One may speculate , however, that if hovering is accompanied by greatly increased wing beat rates, this behavior could effectively isolate the sounds produced by males from the lower frequencies produced by non-hovering females flying past. This acoustical isolation is an essential component if the males are to detect the sounds of females. This phenomenon has been well documented for mosquitoes (Farb , 1962).

Relation of Wing Beat _ Rat~_!_Q_Jjabitat Figure 16 shows the regression line calculated for the relationship of wing lengths to wing beat rates of individual tabanid specimens between 26 and zs0 c. The plotted points are of species' 44 means. When examining the species which fall away or deviate greatly from the regression line, the following species stand out:

SPECIES cps AWAY FROM THE REGRESSION LINE Chrysops callidus +22 Atylotus bicolor +28 Tabanus quinguevittatus +8 Tabanus sparus milleri +12 Hybomitra miniscula -10 Hybomitra microcephala -12 Hybomitra difficilis -10

Tabanus ~erjumentarius -6

(The average standard deviation from the mean wing beat rate is ~10.) A review of the habitats and distributions of these species. supplemented with personal experience, leads to an interesting generalization: Those species which are habitat-restricted to bogs or marshes, or those which occur primarily in wooded areas (this includes most of the ~hyrsops) have consistently lower average wing beat rates, while those occurring in more open areas, with widespread distributions (the more pestiferous species) have consistently higher than average wing beat rates. All of these species seem to have the capacity of flying at normal rates, but perhaps they are behaviorally adapted so that their flight speed is better suited to their habits and habitats. 45

Concluding Remarks The flight sounds of 39 species of Tabanidae have been described, and the various factors which could influence the production of sound are discussed. Table 3 lists all of those factors which have been identified in the literature and in this study. Although wing beat rate is correlated with wing length and body mass, one cannot utilize a single parameter to predict the wing beat rate. Distinct differences occur among several of the species recorded~ and their differences must be examined individually to determine whether their wing beat rates deviate from the expected values due to physical differences, physiological factors, behavioral idiosyncracies, or all three. No inference of biological significance of tabanid flight sounds can be made from the data collected. Although some species appear to produce unique sounds, the sounds of most of the species recorded overlap to some degree. However, now that these sounds have been described, playback experiments in search of behavioral reactions such as those attempted with Asilidae by Lavigne and Holland (1969) should be attempted. The possibility exists that the behavioral response to sound is part of a behavioral sequence, and that without the other stimuli, visual and perhaps chemical, sound alone elicits no response. Data generated to explain the physical factors influencing flight sounds serve additional functions other than the attempted inference of biological significance. Sounds generated by flapping wings describe flight, and flight in tabanids has multiple functions: 46 dispersal, seeking a blood meal and carrying it away, seeking other energy sources (nectar), and perhaps locating and coupling with a mate for reproductive purposes. Describing the average flight of various species yields information regarding their capacity to achieve these functions. By correlating sounds with physical parameters (wing length, wing area. body mass, wing loading, effective aerodynamic center), properties of these species have been described which are often not found in taxonomic literature, but which may be useful to workers in the area of medical and veterinary entomology attempting to determine the importance of one tabanid species relative to another. 47

TABLE 3 Factors Influencing the Sounds of Tabanidae (Diptera)

Aerodynamic Factors: Wing Morphology - Length, Width (Chord), Area Shape, EAC Body Construction - Body Mass, Mass of Flight Muscles Wing Loading - Body Mass I Wing Area Wing Stroke Cycle - Angle of Attack

Environmental Factors: Temperature Light or Time of Day Humidity

Physiological Factors: Physiological Age Energy Available for Flight

Behavioral Factors: Mating Behavior Host Seeking Behavior Feeding Behavior Oviposition Behavior Escape and Dispersal Behavior Habitat Figure 1. Container used for rearing field collected late instar tabanid larvae: Bottom is a paper cup filled with the substrate in which the larvae were collected. Top is a perforated plastic cup with a slightly larger rim diameter.

48 49

Figure 1 Figure 2. Two dimensional modified Malaise trap baited with dry ice and a shiny black sphere for field collecting adult Tabanidae.

50 51

figure '-..,

\ 't Figure 3. Recording chamber - top view with lid removed and leaning against one side: White areas represent inner and outer boxes constructed from plywood. Cross hatched areas are styrofoam, and stippled areas are matted fiberglass ceiling tile. Microphone installation is inserted in a hole cut through the right side.

52 53

Figure 3

::: : : : : : :: : : : :: ::: : :: : : : : : : : : : : : : : :: :~:::: ; [lJtl Figure 4. Specimen holder, constructed of 1/4 in. plexiglass and 1/8 in. diam. plexiglass rods: Specimen holder mount, actually a part of the recording chamber is also pictured. The specimen is resting on the trap door or resting platfonn which can be lowered by pushing down on the stopper on the spring loaded platfonn support rod.

54 55

Figure 4

, CM, I IN

._ . SPECIMEN HOLDER MOUNT AND RUBBER STOPPERS I THERMOMETER :.::w:·1:: P- ~ SPRING- :::l _\::=:;·;:;. :=::{] p.·:1-5::.:=:J

Iri:::::::::::' ~:::m:::::::::~w:,:,, j !\ ; ?J :::::

v TETHERING ROD

- ·~

1--·

L-1 Figure 5. The outline of a tabanid wing: T = tegulum, WSL =wing span line. L = wing length. i = wing segments (n = 10). c. =chord length of 1 segments, ai = length from costal margin to wing span line, dashed line represents the truncation of the wing base for calculations of the effective aerodynamic center, EAC.

56 57

Fi a ure 5 Figure 6. Chrysops cincticornis attached to the tethering rod with rubber cement, resting on the trap door: The thermometer appears in the upper left corner.

Figure 7. Chrysops cinctic2rnis in typical attitude of flight after losinq ground contact with the trap door: Legs are folded and held close to the body, antennae point directly forward .

58 59 Figure 6

I j

Figure 7 Figure 8. Sound production: The vibrating tuning fork (left) produces a displacement of air molecules into areas of rarefaction and condensation. Depicted graphically or by an oscilloscope, the displacement of moleculed translates into a a sine wave with a certain number of cycles or waves per second (cps) (lower left). The sound spectrograph or sonagram on the right is a picture of the sound of a tuning fork of the musical note "A" with a frequency of 440 cps.

60 Figure 8

SOUND PRODUCTION

CONDENSATION - - - ~--.. - -·-~ N 950--""'~--°"'-.,.. I \ ti w. . ~- · w :x: eoo---..,,,._ ~ ___ 0 0 :-:-:-: ~ &so-- o w II)' ffi soo--- 'A' 440cps ~ ' ... :..:...... ·.···"·· . =~=:::::::: =1= ::::~::::::.I ,...,-, .- ... .. ' RAREFACTION , ~0 350---'" > 0 0 t; 200--... z w :> 0 w a: so-- ~ TIME------SOUNO SPECTROGRAPH Figure 9. Flight sounds of Taban idae (Diptera): The tabanid in flight (top left) produces a complicated sound wave (lower left) which is characterized by the loud pulses resulting from the fast upstrokes. The pulsating nature of the wave produces harmonics with frequencies that are multiples of the wing stroke rate . The sonogram on the right is of the flight sounds of a female Tabanus nigr1pes beating her wings at progressively lower rates. Frequency (Hz· or cps) is figured by the Y axis, and timed by the X axis . The lowest frequency band is the fundamental tone or wing beat frequency and the remaining frequency bands are harmonics.

62 Figure 9. Flight sounds of Tabanidae (Diptera) : The tabanid in flight (top left) produces a complicated sound wave (lower left) which is characterized by the loud pulses resulting from the fast upstrokes. The pulsating nature of the wave produces harmonics with frequencies that are multiples of the wing stroke rate . The sonogram on the right is of the flight sounds of a female Tabanus nigripes beating her wings at progressively lower rates . Frequency (Hz or cps) is figured by the Y axis, and timed by the X axis. The lowest frequency band is the fundamental tone or wing beat frequency and the remaining frequency bands are harmonics.

62 Figure 9

FLIGHT SOUNDS OF TABANIDAE ( OIPTERA)

Hz 950-·

eoo-- - · .-"" -· - -- ,. .;r• .I' - ,,; 650-- soo-- -u~..r.r. - ~ · ~ ..- ...... _.._. 350- - --ff5';¥2W1il" ..._.ll~A.iiiil .. Z(llllllll...,...... 200- 4 ... ·-- -...-b!J- w ...... -··· ------so- TIME __.__ ..._ __ ..._ _ _.___ ..._ __ .___

SON AGRAM ONE WING STROKE Figure 10. The relationship of the wing beat frequency to hannonics: As the frequency (Hz) of the fundamental tone increases, the han:ionic overtones increase at multiples of the fundamental frequency. The frequency scale (Y axis) is the "ruler" prepared from the 50 cps or Hz calibration lines shown in the sonogram in Figure 9. The X axis shows the range of wing beat frequencies recorded for Tabanidae, and those reported by Belton and Costello (1979) for mosquitoes.

64 65

Figure 10

...... ~moo ~;_ : _;_ . . " ~950 --:-... : ...... r- t-- ...... §rs~ -!- . . . •T . " J . : . . . . . " _L__ ;;eso ...... " ~·. " .. . _L"Harmon~s lL-": ~800 ...... 3rd l.i,,' ,L/ -.- . . 7 -:- . ~750 ... : i . . __._· .....:7 2nd /" --: : . ~· ,, ~700 .__._ ... . : . . 1st ...... " L ~650 .. . . : .. .. lL" },£/ 3600 ...... ;• /. . ,; ~55() ... : .: ..· .. .. ,, /' ... : ~ ~500 : . . .· . ,; " .L_7 ;; 450 -.. . . . = 1-· ..•• . . _L,, L ~ ~00 . 7-: .. 7 / .. . L . . 7 ~350 . . . ,,' /" = . . . Li ~ ~ 300 .. . ;;;; . ,.' /7 . . -"'- ~ Fundamental ::: 250 .. ,, = . 1" // ~ (Wm aBeaJ FreQu ~c_y) = 200 It_",; L7, ~ :;:1so= = l/'/ ~ =100 ~ ;;so= ~z 100 _____.!SO __ .£®.__ ~ 50 250 300 150 400 Hz TABANIDAt CULICIDAE Figure 11. Average wing beat rates (cps) and standard deviations calculated for 17 species of Pangoniinae: Sample sizes are given in parentheses after the specific names along the X axis (f.. = Chrysops and i· = Stonemyia). Species are listed in decreasing order of wing beat rates.

66 67

Figure 11

• c . ~hu• Ol • s . tranquJJla ()) c. bru,.,,.us ()) - c. rJ•v.l.d1111 (2) • c . •henrt1111.I. Cl) c. vJt:t•tus ())) • c . .l.ndus (3) c. "'"".I. (11) c. bea-rJ (20) c. 11111cqu•rt.I. 119) ii ...._...... c . cuclur C2l

..... c . n1~r C4 l • c. J'.mpunct:us (3) c. un.l.vJ.ttatus 119) c. gem1natus 119) c. c.l.nct:1corn1s 117) • c. call.l.dia 1201

0 0 0 0 0 0 0 0 0 ... .,, M g 0\ e--~...... "' .."' ...... Figure 12. Average wing beat rates (cps) and standard deviations calculated for 22 species of Tabaninae: Sample sizes are given after the specific names along the X axis (Haem. =

Haematopota, ~· = Atylotus, !:!. = Hybomitra, and I· = Tabanus). Species are listed in decreasing order of wing beat rates irregardless of wing length or wet weight.

68 69

Figure 12

• :r. atratu.s ( l) .....--.. :r . ca lens (2)

:r. nigrescens (3)

:r. sackenJ. (6)

:r. superj111Dentarius (17) • T • sulcifrons (14) H. difficilis (4)

H. mi crocephala (3)

Haem. rara (5)

:r. trilllilculata (17)

T. reinwardtii (3) H. minis cul a (27) ~l T. similis (8)

H. sodalis (5)

T . quinquevittatus (24)

H. l11siophthal111a (17)

:r. nigripes (28) • H• pechwnani (l) :r . pW!Ulu.s (16)

A. ohioensis (8)

:r. sparus ll!illeri (18)

JI. bi color (6)

.. c 0 0 0 0 C' 0 0 ,... g N ~ 0 ~ "'"'u-' ~ ~ -"' : - ...... Figure 13. Sonogram of Chrysops vittatus (female) showing the fundamental tone or wing beat frequency {Hz or cps) and 5 harmonic overtones. Other frequency bands are overtones at 1/2 the distance between the fundamental and the first harmonic and between each of the other harmonics.

70 71

Figure 13

950 5th Harmonic lr,-..._.___.____ _.._,.~-- ...... ,_..,--...-_..--·------....~ r 850

4th Harmonic

--- ... - ··

1st Harmonic 250

' ~ ---~·------1so.,...... ,...... F~un•d•am_..e•n•t~a•1-......

so-t------...;;;--...;.;· · ~· ~~~-~~· -=-;:::::;.______..._ __ __

Seconds Figure 14. The effect of temperature changes on the wing beat rates of individual tabanid specimens : A rise in ambient temperature (X axis) of 1°c results in an average increase of 3.4 Hz or cps of the fundamental tone or wing beat rate (Y axis). Line 1 is from a female Chrysops cincticornis and has a slope of 3.74. Lines 2, 3, 4, and 5 are off. beameri with slopes of 4, 4.8, 2, and 0.91, respectively. Line 6 is from a female C. vittatus with a slope of 5, and line

7 is of a female Tabanus quinguevittatu~ with a slope of 2.16.

72 73

Figure 14

1 ~6

100

&G'-:----.23____,2~4~2~s---2s~2-1~2-a~29~~30~3-1~~~-33~-34--.3s°C Figure 15. The effect of temperature range and sample size on the presentation of results: These graphs were constructed from the species averages for wing beat rate (Y axis) and wing length (X axis) of specimens recorded at three different temperature ranges; 101 specimens were recorded at temperatures less than 26°c, 229 specimens between 26 and 2s 0c, and 89 specimens above 2B 0c. Note the increased clustering of data points in the 26 to 2B0 c graph.

74 Figure 15 180 75

170 Temperature Range <26°c + Pangoniinae 160 •• • Tabaninae 150 .. 140 .. ~ •• + 130 • • • • 120 • • • • • 110 • • • 100 • • 90 180 6 10 14 18 20 Ul 2a0 c c.. 170 Temperature Range 26 to 0 • ~ 160 •• N + =150 • • ..,CV 140 •·i IO .. • M • •• • • • .., 130 .. IO • CIJ • .0 120 •• • • O" • -~ 110 3 100 180 6 10 14 18 20 170 • Temperature Range >2B0C 160 + • • • • • 150 • • • 140 • 130 + • • • 120 • • • • • • 110 • 100 wing length (mm) • 90 6 10 14 18 20 Figure 16. The relationship between mean wing beat rates (Y axis) and mean wing lengths (X axis) of 12 species of Pangoniinae and 20 species of Tabaninae: Pangoniinae are represented by open, starred circles and a dotted regression line with the formula Y = 344.7B2x-0·464 , and Tabaninae are represented by black dots and correspond to the dashed regression line with the fonnula Y = 2.88.712x-0· 316 . These lines were calculated from 40 pangonine specimens and 103 tabanine specimens, and the correlation coefficients for both lines are significant to the alpha level of 0.01. Numbers associated with each point refer to species and mean values of wing length and wing beat frequency listed in Table 2.

76 Figure 16

200

175 .l6 20 :c.... • <>'4 0150.. •(/ • 9 31-- •••• ./'.:_ --• -- l2 22 I/) .,....._16v -- •• Q. v• ••• _Al _,.,, - •" .£, •V~V 5 25 -- 23 14 ··,. ---...:29 i --- 100

5 6 1 8 9 10 11 12 13 14 15 16 17 18 19 20 25 Wing length (mm) Figure 17. Wing beat rate and wing length relationships of Tabanidae and Culicidae, and Greenewalt's (1962) boundary line: Regression line for Chrysops and Tabaninae are the same as those in Figure 16, however, here the regression line calculated for 13 species of Canadian mosquitoes (Y = 822x-0·725 ) by Belton and Costello (1979) is also included. Greenewalt's boundary line represents an upper limit for insects for which values of wing length and wing beat frequency were available in the literature.

78 Figure 17 1000 .. .. 900 .·. . 800 ... 700 .. +cmeans of .. Tabaninae 600 .. ·.~ ··~~ ··"--~~ ··"'!-:-• .r-. ···~~ ·.~ ·. ( . ·.~...... •

100 ••••. .. 90 ·.. 80 •• .• 70 ...... 2 20 30 40 50 60 Figure 18. The effect of increased wing length (X axis) on wing shape (Y axis): The shape factor is the square root of the average wing area divided by the average wing length for each species. Points falling below the regression line represent species with narrower wings relative to species represented by points which fall above the line. Numbers associated with each point refer to species listed in Table 2. Solid points are those of Tabaninae while open starred circles are for Pangoniinae. 81

Figure 18

.53

.52 <>n " <} .J2 .51 ~7 ~o

E ~p ~50 ~.. 0 l49 ... .,, u. e20 fl' & ••• Ill •• 27 ~ .io 9• • .48 <>-' .40

.25 .24 .22 .2• .47

.46 .2•

6 8 10 12 14 16 18 20 22 24 Wing Length lmml Figure 19. The relationship of wing length (X axis) to body weight (Y axis): Lines A and D are those calculated by Greenewalt (1962) for birds (Y = 5.3lox0· 3449 ) and insects (Y = 2.4817x0·3376 ), respectively. Lines 8 and C were calculated for Pangoniinae (Y = 4.0538x0· 2433 ) (open circles) and Tabaninae (Y = 2.8433x0· 3350 ) (closed circles), respectively.

82 Fi!_!urc 19

30 ...... •...... A • 20 ...... · ...... 'E 1s ...... E ...... ··o - ...... £ ...... OI ...... ~ 10 ...... _J ...... 9 ...... en ...... c 8 ...... ~ 7 ...... 6 ...... 5 ... 4 6 8 10 20 40 60 80 100 200 300 400 Body Weight (mg)

00 w SUMMARY

A recording chamber, in which flies were tethered in a fixed position and induced to display flight behavior, was designed and constructed to record the wing beat or flight sounds of horse and deer flies (Diptera, Tabanidae). A total of 420 specimens, representing 39 species in 6 genera was recorded, sonographed, and analyzed. Elements of tabanid flight sounds as presented in sonagrams include the fundamental tone or wing beat frequency, harmonic overtones which have frequency levels at multiples of the fundamental, occasional non-harmonic overtones, and loudness with an apparent ability of flies to change the intensities of the other elements in sound. Because of the effect of temperature on flight sound, an average increase of 3.5 cyclespersecond per one degree centigrade increase in temperature, only recordings of specimens made between 26 and 2a0 c were used for analysis. Of those parameters measured, wing length had the highest significant correlation to wing beat frequency. Two regression lines, one for Pangoniinae (Chyrsops and Stonemyia) and one for Tabaninae (Haematopota, Atylotus, Hybomitra, and Tabanus), were calculated. Wing beat frequency means for various species were found to have an average standard deviation of 10 cps. The means of a few species were found to deviate from the regression line by more than one standard deviation. These results indicate that a single parameter

84 85

{wing length) is not sufficient for predicting the wing beat rates of all Tabanidae. Wet weight was also found to be significantly correlated with the wing beat frequencies of tabanine specimens. The effect of size was also determined: In general, as the wing length increases, wing loading increases and wings become narrower {the shape factor decreases). The expected effects of these scale phenomena initially appear to contradict the observed decrease of wing beat frequency with increased size. This decreased wing beat rate, however, is probably due to the resonant mechanical frequency of the wing and wing articulation structures which also tend to decrease with an increase in size. Various species, particularly Chrysops sp., were found to have different wing loading shape factor values than other species such as Tabanus sp. of comparable size, and these differences may be used to explain their deviations from the wing length vs. wing beat rate regression line. Seven of the eight male specimens recorded and sonagraphed had higher wing beat rates than the means of their respective females. Bog or forest restricted species such as Hybomitra miniscula and !:!_. difficilis had lower than expected wing beat rates while pestiferous species found in open areas such as Chrysops callidus and Tabanus quinquevittatus had higher than expected rates. These results suggest possible sexual and habitat related behavioral differences which could override the morphological factors influencing the production of sound. APPENDIX A

Pangoniinae: Stonemyia tranguilla (Osten Sacken): Roaring Plains, Randolph Co., WV, (2 females, 1 male) 4 Aug. 1979. fhrysops beameri Brennan: Cedar Bog, Champaign Co., OH, (1) 30 July 1979, (18) 13 Aug. 1979, (2) 27 Aug. 1979. Chrysops brunneus Hine: Mentor Marsh, Lake Co., OH, (3) 18 July 1978. Chrysops callidus Osten Sacken: Rockmill Dam Reservoir, Fairfield Co., OH, (1 reared) 10 May 1978, (5) 5 June 1978; Green Tree Acres, Delaware Co., OH, (6) 15 June 1978; St. Joseph's River, Williams Co., OH, (2) 20 June 1978; Secrest Arboretum, Wayne Co., OH, (1) 23 June 1978; Cedar Bog, Champaign Co., OH,

(1) 26 June 1978, (1) 2 July 1979, (1) 9 July 1979, (1) 30 July 1979, (1) 27 Aug. 1979.

86 87

(1) 18 June 1979, (1) 25 June 1979. Chrysops geminatus Wiedemann: Cedar Bog, Champaign Co., OH, (5) 26 June 1978, (3 females, 1 male) 25 June 1979, (1) 2 July

1979, (4) 11 July 1979, (6) 16 July 1979, (1) 23 July 1979. Chrysops impunctus Krober: Cedar Bog. Champaign Co., OH, (3) 2 July 1979, (2) 16 July 1979. Chrysops indus Osten Sacken: Pymatuning Lk., Ashtabula Co., OH,

(1) 7 June 1978; St. Joseph 1 s River, Williams Co., OH, (1) 20 June 1978; Cedar Bog, Champaign Co., OH, (1) 2 July 1979. Chrysops macguarti Philip; Secrest Arboretum, Wayne Co., OH, (5) 24 June 1978; Cedar Bog, Champaign Co., OH, (5) 26 June

1978, (1) 2 July 1979, (2) 11 July 1979, (6) 16 July 1979. Chrysops moechus Osten Sacken: St. Joseph's River, Williams Co., OH, (1) 20 June 1979. Chrysops niger Macquart: Rockmill Dam Reservoir, Fairfield Co., OH, (1) reared) 10 May 1978, (2) 5 June 1978; Cedar Bog, Champaign, Co., OH, 25June 1979. 88

Chrysops pikei Whitney: St. Joseph's River, Williams Co., OH, (3) 20 June 1978; Cedar Bog, Champaign Co., OH, (1) 16 July 1979, (3) 23 June 1979, (2) 30 July 1979; Rockmill Dam Reservoir, Fairfield Co., OH, (1 male reared) 15 June 1978. Chrysops shermani Hine: Cranesville Swamp, Preston Co., WV, (1) 14 Aug. 1978. Chrysops univittatus Macquart: Secrest Arboretum, Wayne Co., OH, (1) 24 June 1978; Cedar bog, Champaing Co., OH, (9) 26 June 1978, (5) 16 July 1979, (1) 30 July 1979, (2) 13 Aug. 1979, (1) 27 Aug. 1979. Chrysops vittatus Wiedemann: Secrest Arboretum, Wayne Co., OH, (10) 24 June 1978; Cedar Bog, Champaign Co., OH, (4) 26 June 1978, (1) 2 July 1979, (2) 11 July 1979, (13) 16 July 1979, (1) 30 July 1979, (2) 13 Aug. 1979.

Tabaninae: Haematopota rara Johnson: Cedar Bog, Champaign Co., OH, (3) 26 June

1978, (2) 2 July 1979~ Cranesville Swamp, Preston Co., WV. (1) 5 Aug. 1979. Atylotus bicolor Wiedemann: Cedar Bog, Champaign Co., OH. (1) 26 June 1978, (3 females, 1 male) 30 July 1979, (1) 6 Aug. 1979. Atylotus ohioensis (Hine): Cedar Bog, Champaign Co., OH, (1 male)

25 June 1979, (1) 11 July 1979, (1) 16 June 1979, (1) 23 July 1979, (4) 30 July 1979. 89

Hybomitra difficilis(\~iedemann): Tar Hollow St. Pk., Ross Co., OH, (4) 10 June 1978. Hybomitra lasiophthalma(Macquart): Tar Hollow St. Pk., Ross Co., OH, (1) 10 June 1978; Secrest Arboretum, Wayne Co., OH, (1) 24 June 1978; Cedar Bog, Champaign Co., OH, (7) 26 June 1978, (2)

11 June 1979, (1) 18 June 1979, (1) 25 June 1979, (3) 2 July

1979, (1) 23 July 1979. Hybomitra microcephala(Osten Sacken): Cranesville Swamp, Preston Co., WV, (3) 14 Aug. 1978. Hybomitra miniscula(Hine): Cranesville Swamp, Preston Co., WV,

( 10) 12 Aug . 19 78 , (17) 5 Aug . 19 79 . Hybomitra pechumani Teskey and Thomas: Cranesville Swamp, Preston

Co., WV, (1) 5 Aug. 1979. Hybomitra sodalis Williston: Cedar Bog. Champaign Co., OH, (1) 25 June 1978, (3) 11 July 1979; Cranesville Swamp, Preston Co., WV, (1) 5 Aug. 1979. Tabanus atratus Fabricius: Cedar Bog, Champaign Co., OH, (1) 13 Aug. 1979. Tabanus calens Linnaeus: Delaware Lk. Public Hunting and Fishing Area, Delaware Co., OH, (1) 22 Aug. 1978; Henry Co., OH, (1) 23 Aug. 1978. Tabanus nigrescens Palisot de Beauvais: Cedar Bog, Champaign Co.,

OH, (2) 16 July 1979, (1) 6 Aug. 1979. 90

Tabanus nigripes Wiedemann: Cedar Bog, Champaign Co., OH, (4) 26 June 1978, (4) 2 July 1979, (2) 16 July 1979, (8) 23 July 1979, (6) 30 July 1979, (2) 6 Aug. 1979, (1) 13 Aug. 1979. Tabanus pllTlilus Macquart: Cedar Bog, Champaign Co., OH, (2) 26 June 1978, (2) 2 July 1979, (7) 11 July 1979, (3) 16 July 1979, (1) 23 July 1979. Tabanus guinguevittatus Wiedemann: Tipton Lane, Scioto Co., OH, (3 females, 2 males) 14 June 1978; Cedar Bog, Champaign Co., OH, (1) 26 June 1978, (2) 11 July 1979, (4 females, 2 males) 23 July 1979, (2) 30 July 1979, (4) 6 Aug. 1979, (3) 13 Aug. 1979. Tabanus reinwardtii Wiedemann: Rockmill Dam Reservoir, Fairfield Co., OH, (1 male, 1 female reared) 19 June 1978; Cedar Bog, Champaign Co., OH, (1) 30 July 1979. Tabanus sackeni Fairchild: Cedar Bog, Champaign Co., OH, (1) July 1979, (1) 6 Aug. 1979, (2) 13 Aug. 1979, (2) 27 Aug. 1979. Tabanus similis Macquart: Cedar Bog, Champaign Co., OH, (1) 18 June 1979, (1) 11 July 1979, (1) 16 July 1979, (2) 30 July 1979, (2) 6 Aug. 1979, (1) 13 Aug. 1979. Tabanus sparus milleri Whitney: Secrest Arboretum, Wayne Co., OH, (1) 14 June 1978; Cedar Bog, Champaign Co., OH, (1) 26 June 1978, (1) 11 June 1979, (1) 15 June 1979, (1) 2 July 1979, 91

(2) 11 July 1979, (4) 16 July 1979, (5) 23 July 1979, (3) 30 July 1979. Tabanus sulcifrons Macquart: Delaware Lk. Public Hunting and Fishing Area, Delaware Co., OH, (1) 22 Aug. 1978; Cedar Bog,

Champaign Co., OH, (1) 16 July 1979, (1) 30 July 1979, (8) 6 Aug. 1979, (3) 13 Aug. 1979. Tabanus superjumentarius Whitney: Cedar Bog, Champaign Co., OH, (6) 26 June 1978, (2) 25 June 1979, (5) 11 July 1979, (3) 23 July 1979, (1) 13 Aug. 1979. Tabanus trimaculata Palisot de Beauvais: St. Joseph's River, William Co., OH, (1) 20 June 1978; Secrest Arboretum, Wayne Co., OH, (2) 24 June 1978; Cedar Bog, Champaign Co., OH, (2) 26 June 1978, (1 male) 25 June 1979, (1) 2 July 1979, (4) 11 July 1979, (3) 16 July 1979, (1) 23 July 1979, (2) 30 July 1979. Tabanus vivax Osten Sacken: Roaring Plains, Randolph Co., WV, (1) 4 Aug. 1979. APPENDIX B Flight Mode of Diptera

There are two extreme modes of flight to consider: no forward speed, only flapping, and high speed glide without flapping. All actual cases will lie in between these two modes. Analogous to helicopter rotor analysis, one can express the flight state in terms of an advanced ratio, µ:

_ forward velocity (v) µ - maximum flapping velocity (Wmax)

If µ = 0, then the insect has no forward speed.

Ifµ = ~. the insect glides without flapping. Ifµ = l, the maximum tip speed equals the forward velocity. A typical advanced ratio for an insect flying at a speed of v = l5 feet/sec., with a wing span of 2 inches, a wing beat frequency of .00 cps (628 rad/sec), and a wing stroke angle of 80 degrees (1.396 ·adians) isµ= v/Wmax = 15/73 = 0.205 (Wmax = 1.396·1/12·628). It is hus shown that µ is considerably smaller than l, and therefore using = 0 is an acceptable approximation of dipteran flight.

92 APPENDIX C Sample calculatien of the effective aerodynamic CP.nter; Chrysops brunneus

2 3 2 -i --Ci(mm) Ci (mn/WSL) (i·!i) (i·Ji) (i·'t)3ci (i ·Ii) ci ai (lTITI) ai(imv'WSL) ai-r.ci [(i·'t) 2] [ai-liCil 1 0.8 0.9 0.25 0.13 0.11 o.n 0.2 0.23 0.01 0.001 2 1.9 2.16 2.25 3.38 7.29 4.86 0.3 0.34 ·0.2 -0.972 3 2.6 2.95 6.25 15.63 46.09 18.44 0.5 0.57 -0.17 -3.135 4 3.0 3.41 12.25 42.88 146. 20 41. 77 0.6 0.68 ·0.17 . 7 .101 5 3.2 3.64 20.25 91.13 331. 70 73.71 0.85 0.97 0.06 4.423 6 3.2 3.64 30.25 166.38 605.61 110.11 0.9 1.0 0.09 9.910 7 3.2 3.64 42.25 274.63 999.64 153. 75 1.0 1.14 0.23 35. 363 8 3.0 3.41 56.25 421.88 1438.59 191.87 1.2 1.36 0.51 97. 823 9 2.5 2.84 72.25 614.13 1744.12 205.19 1.1 1.25 0.54 110.803 10 1.4 1.59 90.25 857.38 1363.23 143.50 0.7 0.80 0.09 12.915 I--- I-- I--- 6682.58 943.43 260.03

(EAC) = 6682.58 = 0.78, 70.8%, or 6.23 mm from the tegulum along the 5 943.43 Wing Span Line (WSL).

(EAC) = 260 .03 = 0.027, 2.76%, or 0.24 mm in front of the Wing Span c 943 .43 Line (WSL) •

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