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University Micixxilms International 300 N. ZEEB ROAD, ANN ARBOR, Ml 48106 18 BEDFORD ROW, LONDON WC1 R 4EJ, ENGLAND 8022260

DREES, BASTIAAN MEIJER

THE BIOACOUSTICS OF TABANIDAE CDIPTERA)

The Ohio State University PH.D. 1980

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University Miodffiims irtternarional 200 N Z=== PO. ANN AR30P 48106 '313! 761-4700 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 7 Adviser Dr. Donald J. Borror Department of Entomology 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 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 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. Born, Amsterdam, Netherlands

B.A., Biology with minors in Chemistry and Art, West Virginia University, Morgantown, WV.

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.

Insect Specialist, identifications and control recommendations, assisting Dr. J. F. Baniecki, West Virginia Cooperative Extension Service, West Virginia University Morgantown, WV.

Andrew Delmar Hopkins Scholarship in Entomology, West Virginia University, Morgantown, WV.

M.Sc., Entomology, West Virginia University Morgantown, WV.

Teaching Associate, Economic Entomology, The Ohio State University, Columbus, OH.

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.

Teaching Associate, General Biology, Department of Zoology, The Ohio State University, Columbus, OH. 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 Information 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 Information Series 96. Cooperative Extension Service, West Virginia University, Morgantown, WV.

Drees, B. M. 1977. in 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. in The Cooperative Plant 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. In 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. TABLE OF CONTENTS

Page

ACKNOWLEDGEMENTS ...... 11

VITA...... iv

LIST OF TABLES...... ix

LIST OF FIGURES...... x

INTRODUCTION ...... 1 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 A r e a...... 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 H ab itat...... 43 Concluding Remarks...... 45

SUMMARY...... 84

APPENDIX

A. Collection Data for Specmens Recorded ...... 86

B. Flight Mode of D i p t e r a...... 92

C. Sample Calculation of the Effective Aerodynamic Center, 93

BIBLIOGRAPHY ...... 94

vi i i 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 28 C for Thirty-nine Species of Tabanidae ...... 29

3 Factors Influencing the Sounds of Tabanidae (D iptera)...... 47

i.x LIST OF FIGURES

Figure Page

1 Container used for rearing field collected late instar tabanid l a r v a e...... 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 s i d...... e 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 d o o...... r 58

7 Chrysops cincticornis in typical attitude of flight after losing 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 harmoni 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 5 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 a x i s ) ...... 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 a l., 1975; Bennet-Clark and Ewing,

1968 and 1970; Waldron, 1964; and Webb et a l., 1976), Tephritidae

(Sharp and Webb, 1977), and Glossina (ICIPE, 1974; Popham et a l., 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 deer flies (Diptera, Tabanidae)

with a consideration for the factors which influence the sounds

produced.

1 2

Literature Review of Tabanid Sexual Behavior arid 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 a l. 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, i t would be a behavioral disadvantage to spend much energy to pursue and contact other species before locating a mate. Pheromones may also play an important role in sexual recognition of Diptera

(Cowan and Rogoff, 1968; Ubel et a l., 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 cincticorn!s 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 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. 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 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 ’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). TABLE 1 Observations of Tabanid "Courtship" Flights

Flight Copulation Species Observer Flight Dates Time of Day Heights Observed

Tabanus americanus Hasemann (1943) 9 Sept - 15 Sept 7:00 p.m. 3-5 f t. No (qlqanteus) 30 3 ft. candles T. americanus Hagmann e t a l. 10 Aug - 12 Aug 7:20-8:10 p.m. 2-5 f t. Yes (qlqanteus) (1947) to 20 f t . T. sulclfrous Hasemann (1943) 27 duly - 2 Sept 5:30 a.m. 30 f t . No 1 to 3 or 5 ft. above trees candles. 20-25 m. . no courting below 60 T. sulclfrous Hlne (1903) la te duly & before 9:00 a.m. south side Yes through Aug of woods T. thorasleus 7 Haddow et al. not stated nautical twilight not stated 7 (1961) Uganda ■til sun 1s 12® rain forest below horizon T. Inslqnls 7 Haddow e t a l. not stated arrives 25 mln. not stated 7 (1961) Uganda la ter rain forest T. phaneops Hebb and Hells not stated 8-9:00 p.m. not stated 7 (1924) Hybomltra aurlllmbas Blickle (1955) 6 duly - 30 duly 9 a.m. - 5:00 p.m. 1-3 f t . No H. clncta Bailey (1948) 7 duly - 29 duly 8:30-9:40 a.m. 1-4 f t . No 1:30-5:10 p.m. H. 11lotus Philip (1931) 11 duly - 12 duly 9:30 a.m.- males perched No 12:00 noon on vegetation Chrysops fulglnosa MacCreary (1940) 9 dune - 10 June 9-10 a.m. mating pairs Yes resting on aquatic vegetation T. relrmardtll JLavlgne, Bloom 26 dune - 4 Aug 7:27 n. 11:02 a.m. coupling In air Yes and Neys (1968) from 3 In. to 5 f t . high sometimes accompanied by brief hover C. fulvaster Lavlgue, Bloom 13 dune - 7 Aug 7:45 * 10:23 a.m. males coupled with Yes and Neys (1968) female 1n flig h t Actual mating was observed for Tabanus americanus (= giganteus) by Hagmann et a l. (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 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, 1975), flight velocities and other characteristics of the opposite sex. However, i t 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 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 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. illbtus were noticed in the same location. The five ... diminished to one about noon. They varied their position within this space but always returned to i t 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 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, C. niger, C. 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 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 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 temperature as cool as possible during field recordings.

The chamber was constructed around a Freeze Safe Polyfoam Packers

Co. insulated container. This structure was firs t 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 f i t 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 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, T. calens,

T. 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

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 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.

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 -4 on a Mettler Type H16 Balance to the nearest 10 g in order to determine the wet weight or body mass. Flies were weighed individually to prevent thawing, and then they were placed quicklyin2 dram

(17 x 60 mm) Kimble Shell Vials and sealed in with Parafilm "M"

Laborotory Film. Vials were stored at -18°C in a Sears Coldspot

Frost!ess refrigerator-freezer. Some specimens were pinned and mounted rather than being frozen. 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 mm, 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 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 chordm . The point at which chordm,„ occurs is measured at a set max r max 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 2 2 19.84 mm or 2 cm ) piece of Xerox paper, or rather the weight of 1 mm 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 l if t 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 firs t determining the effective aerodynamic center of the span, (EAC)$, 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 angleof 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 counted from the wing base. In the middle of each segment, the chord length, , 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:

where W is the flapping velocity of the wing tip. The aerodynamic max moment at the base of the flapping wing is:

and, the total aerodynamic moment for the wing is obtained by summing the aerodynamic moments of all of the segments:

f L-l/rH1-l/2)3- s> ■ f • r ------— Z{(i-l/2r-C,}I 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 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.

(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: 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) is negative) the wing span line where V 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 complex 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 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 in6 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 T. quinquevittatus.

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 a l., 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). Other non-harmonic overtones occasionally appear in sonagrams.

These include frequency levels ath 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 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, less thanh 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/l°C reported for Aedes degypti 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 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 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 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 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 (26-2S°C) for thirty-nine species of Tabanidae. SPECIES WING LENGTH (mm) WING AREA (mm2) WET WEIGHT (mg) WING LOADING (mg/urn^) WING BEAT FREQUENCY (cps) 26-28°C Pangoniinae: 1. Stoneayia tranquilla10.13* 0.25 (3) 23.81* i;03 (2) 39.10* 3.30 (3) 0.80* 0.11 (2) 2. Chrysops beameri 7.11* 0.37(14) 13.37* 1.27(12) 9.30* 2.30(12) 0.32* 0.06(10) 143.32* 5.90 (5)

3. Chrysops brunneus 8.13* 0.61 (3) 15.95* 2.62 (3) 4. Chrysops callldus 7.65* 0.35(17) 14.41* 1.94(14) 19.40* 5.00 (5) 0.59* 0.10 (3) 157.46* 7.30(13)

5. Chrysops clncticoznis 7.67* 0.61(12) 14.30* 2.47(13) 139.09*12.70 (6)

6. Chrysops cuclux 8.00* 0.42 (2) 14.73* 1.42 (2) 137.13* 5.83 (2)

7. Chrysops flavidus 8.25* 0.21 (2) 17.93* 1.23 (2) 12.30 (1) 0.36 (1) 8. Chrysops geminatus 6.04* 0.49(16) 9.72* 1.35(13) 6.75* 3.40(13) 0.33* 0.07 (7) 153.27* 9.43(11) 9. Chrysops impunctus 6.68* 0.21 (5) 11.31* 0.69 (4) 8.70* 2.40 (4) 0.36* 0.09 (3) 148.65* 0.21 (2)

10. Chrysops Indus 8.27* 0.23 (3) 17.60* 0.90 (3) 16.80 (1) 0.541 (1) 135.00 (1) 11. Chrysops macquarti 7.10* 0.31(19) 13.38* 1.47(17) 8.20* 1.80 (8) , 0.30* 0.08 (6) 136.85*12.04(13)

12. Chrysops noechus 8.0 (1) 17.99 (1)

13. Chrysops niger 6.93* 0.25 (3) 12.07* 1.10 (3) 9.5 (1) 0.39 (1) 142.50* 3.54 (2)

14. Chrysops pikei 7.04* 0.32 (8) 12.48* 1.27 (7) 9.10* 0.70 (5) 0.37* 0.62 (4) 141.20* 7.95 (5)

15. Chrysops shenaani 8.20 (1) 16.57 (1) 132.00 (1)

16. Chrysops univittatus 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 vittatus 7.87* 0.44(28) 15.56* 1.84(25) 11.25* 3.45(11) 0.39* 0.10 (6) 129.69*10.81(23)

Tabaninae

18. Haematopota rara 7.40* 0.23 (5) 13.16+ 1.13 (5) 9.80+ 0.70 (2) 0.36+ 0.06 (3) ro vo SPECIES WING LENGIH ftirfl WING AREA (rim2) WET WEICkT Qng) WING LOADING (mg/mn2) WING BEAT FREQUENCY (cp s) 26-28°C

19. A ty lo tu s bicolor 8.50* 0.56 (5) 17.09* 2.61 (5) 25.70* 7.50 (4) 0.79* 0.21 (4) 174.72* 9.73 (5) 20. Atylotus ohioensis 7.10* 0.43 (8) 12.01* 1.50 (8) 13.95* 9.26 (8) 0.43* 0.09 (8) 158.67* 9.62 (6) 21. Hybomitra d ifficilis 12.37* 0.40 (3) 32.46* 0.55 (2) 119.50* 9.69 (4)

22. Hybomitra pechumani 9.50 (1) 20.16 (1) 45.30 (1) 1.12 (1) 149.17 fl)

23. Hybomitra lasiophthalma 11.01* 0.59C14) 26.17* 2.78(10) 42.90* 9.93 (6) 0.78* 0.13 (4) 137.92* 8.25 (2)

24. Hybomitra microcephala11.90* 0.66 (3) 32.02* 4.97 (3) 119.43* 2.23 (2) 25. Hybomitra mlniscula 8.72* 0.53(26) 17.26* 2.28(25) 21.96* 6.94(17) 0.68* 0.09(16) 135.19*17.33(20)

26. Hybomitra sodalis 11.60* 0.61 (4) 31.22* 2.76 (4) 76.50*15.79 (5) 1.08* 0.04 (3) 137.04*11.30 (3) 27. Tabanus atratus 23.10 (1) 123.4 (I) 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) 82.73* 6.75 (3) 329.2*13.50 (3) 2.00* 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*23.36(20) 31. Tabanus pumilus 7.28* 0.35(16) 12.88* 1.28(15) 19.60*. 8.16(13) * 0.77* 0.26(13) 154.15*10.16 (8)

32. Tabanus quinquevittatus9.29* 0.42(23) 21.86* 2.05(19) 41.66* 6.99(17) 0.96* 0.07(15) 148.73*16.28(16)

33. Tabanus reim rardtii 13.53* 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* 2.77 (5) 67.28* 0.02 (6) 0.92* 0.10 (5) 123.40*10.47 (2) 35. Tabanus s im ilis 10.34* 0.45 (7) 25.22* 1.90 (7) 44.70*11.58 (7) 0.82* 0.10 (7) 137.25*16.80 (5) 36. Tabanus sparus m iller17.58* 0.32 17) 13.99* 1.38(17) 21.06* 7.50(16) 0.79* 0.14(16) 163.60* 9.93(12) 37. Tabanus su lc i frons 17.50* 1.15(14) 72.57* 4.12 (9) 217.96*25.72(12) 1.56* 0.09 (7) 121.62* 7.21(10)

38. Tabanus superjumentariusl4.19± 0.58(17) 47.18* 4.03(16) 122.18*18.00(11) 1.32* 0.12(10) 118.96* 6.45 (8) 39. Tabanus trimaculata 13.19* 0.71(15) 40.22* 4.88(11) 123.00*29.60(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) 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 of0 .0 1 , 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:

Y = 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 equati on:

Y = 344.782 X ' 0 ' 464

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 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 CUg + 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 chordm3V at 25%. These results have indicated ITiaX 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 (r 70 = = "0*372) nor

Tabaninae (r = u s = "0-666) was more significant than those for wing length and wing beat frequency (r 40 = = "0*551 and rp _ = -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 = 246.01789 X" ° * 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'Vrnm). 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 equati on:

Y = 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) (EAC) ______J L

Chrysops bruneus 9 70.8% 2 .8%

Chrysops bruneus 9 70.7% 2 . 2%

Chrysops bruneus 9 71.1% -

Chrysops cincticornis9 68.9% -

Chrysops cincticornis d* 69.1% -

Chrysops geminatus 9 70.9% -

Chrysops moechus 9 69.3% -

Haematoapota rara 9 70.5% -

Haematoapota rara 9 70.3% -

Hybomitra difficilis 9 69.3% -

Tabanus nigrescens9 69.0% 0.9%

Tabanus nigripes 9 70.1% -

Tabanus quiriquevittatus 9 70.5% -

X = 70.0%

Results indicate small, but consistent differences among species.

As predicted, the more tapered the wing, the more basal the (EAC)g and the closer the (EAC) to the wing span line. However, the minor L 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 a l., 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 thattabanidae, 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 = = -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, T. septentrional is , Chrysops furcata and

C_. 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 Y2,899 or Y = 5.3101 x0' 3449 Insects: X = 0.677 Y2,9617 or Y = 2.4817 x° '3376

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 Y4,1105 or Y = 4.0538 x°*2433

Tabaninae: X = 0.00419 Y2,9863 or Y = 2.8433 x0,3350

(Note that GreenewaIt 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 firs t, 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 Hybomitra frontalis (Walker) (= T. septentrional is ) and H_, aff i ni s (Kirby) by

Miller (1951), and for Tabanus quinquevittatus Wiedemann and X* 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 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) (r _ 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 and2 ) 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 (r =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):

Y = 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, JC. pikei, 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 "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 2 0 0 % 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 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. 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 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 pi euro-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. 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 l if t 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 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 Hybomitra miniscula at Cranesville

Swamp, Preston Co., West 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 Rate to Habitat

Figure 16 shows the regression line calculated for the relationship of wing lengths 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 quinquevittatus +8

Tabanus sparus milleri +12

Hybomitra miniscula -10

Hybomitra microcephala -12

Hybomitra d ifficilis -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 Chyrsops) 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 functtons. 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. 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 / Wing Area Wing Stroke Cycle - Angle of Attack

Environmental Factors: Temperature Light or Time of Day Humi di ty

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

V 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 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 platform which can be lowered by pushing

down on the stopper on the spring loaded

platform support rod.

54 SPECIMEN HOLDER MOUNT AND RUBBER STOPPERS THERMOMETER

SPRING

TETHERING Figure 5. The outline of a tabanid wing: T = tegulum,

WSL = wing span line, L = wing length, i =

wing segments (n = 10), = chord length of

segments, a.' = 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

Figure 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. Figure 6

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

•••• •

iu 500 'A* 4 4 0 cps

RAREFACTION P 350

TIME

TIME-

ONE CYCLE SOUND SPECTROGRAPH

c n 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 (DIPTERA)

Hz 162335 950 • <

800

650

500

350 i UPSTROKE a * ,

200 DOWNSTROKE

50 TIM E - I I I » TIME SONAGRAM ONE WING STROKE

< T t U> 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

• • • • • • ✓ = 1000 • •• • • 1 • • • • y • • • • J E 950 • • •• • • • • • • ✓ ✓ = 900 •• • • • • •• •• y / •' • • = 850 1• • • * • • •• rmomcs /; /, / H a 800 •• • • ✓ s • • .*l 3rd * 750 • • • •* • • • I •• s s • m • • • ' * . / 2nd X ss ■■ i ; l 1' • * • ✓ 700 •• •• • • • • • • « ✓ 1st • t • •• 650 * * ; • • • • / 600 • • • • • y E • • • : ; / / ✓ ✓ = 556 '••••••• .* • • / / ✓ 500 • • * • J • = •• •• • • • • • • 450 ; • • •’ — • / .• .* / 400 • • • • = * • .• .* ✓✓ • • •• ✓ 356 • .• • • • .• ✓ / E 300 // Fundamenta = 256 / (Wina Beat Freau sncy) = 200 / x 150 = 106 50 Hz 50 100 150 200 250 300 350 400 Hz I a b a n id a I c u l ic id a e 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 axi s (£. = Chrysops and = Stonemyia) .

Species are listed in decreasing order of wing

beat rates.

6 6 67

Figure 11

C. noechus (1) S. tzanguilla (3)

C. brunneus (3)

Cm fla v id u s (2)

Cm shermanl ( 1) C. v itta tu s (33) C. Indus (3)

C. p ik ei (11) C. beaoeri (20)

C. nacgua rt! (19) SPECIES C. cuclux (2)

C. itig e r (4)

C. impunctus (3)

C. unlvittatus (19)

C. geminatus (19)

C. c ln c tlc o rn is (17)

C. c a llid u s (20) 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, A. = Atylotus, li = Hybomitra, and

T. = Tabanus) . Species are listed in decreasing

order of wing beat rates irregardless of wing

length or wet weight.

68 Figure 12

T. a tra tu s (1) r . calans (2)

T. nigrescens (3) r . sackenl (6)

T. suparjumentarlus (17)

T. sulcitrons (14)

H. difficllis (4)

H. mlcrocephala (3)

Haam. rara (5)

T. trimaculata (17)

T. relnwardtil (3) in Mfid H. sd niscula (27) ^ & r . a im ilia (s)

a. so d a lls (5)

T. qvinquevittatus (24)

B. laslophthalna (17)

T. nlgrlpas (28)

a. pechumani (1)

T. pumllus (16) 4. ohloansis (8)

T. spams millaxl (18)

A. b lc o lo t(6) 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 Figure 13

950 -H 5th Harmonic 850

750 !*• 4th Harmonic iF 650 ip & 3rd Harmonic 550 fii* I 450 2nd Harmonic

350* ■ 1st Harmonic 250 »

Fundamental 150 ■

5 0* —\------T S e c o n d s 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 C. beameri with slopes of 4,

4.8, 2, and 0.91, respectively. Line6 is from

a female C. vittatus with a slope of 5, and line

7 is of a female Tabanus quinquevittatus with a

slope of 2.16.

72 73

Figure 14

190]

180]

150i

N140

130]

120

110 100 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; 1 0 1 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 wing beat rate (Hz or cps) 170 100 0 1 1 120 180- 130 140. 150. 160 180 140- 100 110 130- 150- 160- 170- 180. 120 120. 130- 140. 150. 160. 170- 110 100 90. 90 - - . . - - - 6 6

10 10

iglnt (mm) length wing Temperature Range <26°C Range Temperature Temperature Range 26 to 28°C to 26 Range Temperature Temperature Range >28°C Range Temperature iue 15 Figure • • • 4 18 14 14 14

Pangoniinae ♦ • Tabaninae 18 18

20 20 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“^ ’^ , and Tabaninae

are represented by black dots and correspond to

the dashed regression line with the formula

Y = 2.88.712X~^'^®. 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 Wing Beat Rate (cps or Hz) - 0 0 2 100 150 175 125 80* 0 9 — - - - - J —i —i —i |—i i i'l l i i | i i i i | l l ' i i | i i r i— — | i r i— i— — | i— I— i— i— "J— 5

6 o'

7

6 3 8

9 ig egh (mm) Length Wing 10 ------

iue 16 Figure 1 ------11 1 ------

31 * 1 .3 - » —|—r—|—i —i —|—i —i i i— I— i— — | i— — | i— j— i— — | — r — | 1— 12 *21 M *

13 c

14

15

16

17

J7 18 --

| i-| - i | i 19

20 ------

M • 1 ------—i 1— ------—■ 1— 25 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"®*^)

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 1000-1 900- 800- 700- ♦=means of Tabaninae 600- *•<£ c 500-1 uo 0> wk. 400-1 0) , Q. 4 (A ••a . "30 0 0 H % > S O 1

© 200- © cc

© CD a t

100- 90- 80- 7 0 - ~r 1 ■—r - | -*i---- 1--- 1 | i - 1 2 1—I ! i)iU 1 20 30 40 50 60 Wing Length - millimeters

VO 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 45 .

. 8 4 Shape Factor 31 49 46 47 - - - - 31.55 ,10 .3* .3* .00 .50 iue 18 Figure ig egh Imml Length Wing 81 \

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 = 5.310X0*3449) and insects (Y = 2.4817X0,3376^,

respectively. Lines B and C were calculated for

Pangoniinae (Y = 4.0538X®'^433) (open circles) and

Tabaninae (Y = 2.8433X®’333^) (closed circles),

respectively.

82

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 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 (Chyrsops and Stonemyia) and one for Tabaninae (Haematopota, Aty1otus, Hybomitra, and Tabahus), 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 d ifficilis 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 tranquil!a (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 macquarti 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 nioechus 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, 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 d iffici1i s (Wiedemann): Tar Hollow St. Pk., Ross Co., OH,

(4) 10 June 1978. 4 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.

Hybomi tra mi crocepha1 a(Osten Sacken): Cranesville Swamp, Preston Co.,

WV, (3) 14 Aug. 1978.

Hybomitra miniscula(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. 1979.

Hybomitra soda!is 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 Pali sot de Beauvois: 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 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 quinquevittatus 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 Beauvois: 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, y:

______forward velocity (v) y = maximum flapping velocity (W~T ITlaX )

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

If y = % the insect glides without flapping.

If y = 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 y = v/Wm=v = 15/73 = 0.205 (Wmav = 1.396-1/12-628). It is ITlaX IllaX thus shown that y is considerably smaller than1 , and therefore using y = 0 is an acceptable approximation of dipteran flight.

92 APPENDIX C : Sample calculation of the effective aerodynamic center; Chrysops brunneus

EAC

0.6mm 2.6 3 .0 3 .2 3 .2 3 . 0 2 .5

i Cj,(mm) Ci(nm/WSL) ( i - W 2 ( i - W 3 ( i - W ^ ( i - W 2 ^ (in n /W S L ) a i * W j

1 0 . 8 0 . 9 0 . 2 5 0 . 1 3 0 . 1 1 0 . 2 3 0 . 2 0 . 2 3 0 . 0 1 0.001

2 1.9 2.16 2.25 3 . 3 8 7 . 2 9 4 . 8 6 0 . 3 0 . 3 4 - 0 . 2 - 0 . 9 7 2

3 2 . 6 2 . 9 5 6 . 2 5 1 5 . 6 3 4 6 . 0 9 1 8 . 4 4 0 . 5 0 . 5 7 - 0 . 1 7 - 3 . 1 3 S

4 3 . 0 3 . 4 1 1 2 . 2 5 42.88 146.20 41.77 0.6 0 . 6 8 - 0 . 1 7 - 7 . 1 0 1

S 3 . 2 3 . 6 4 2 0 . 2 5 9 1 . 1 3 3 3 1 . 7 0 7 3 . 7 1 0 . 8 5 0 . 9 7 0 . 0 6 4 . 4 2 3

6 3 . 2 3 . 6 4 3 0 . 2 5 166.38 605.61 1 1 0 . 1 1 0 . 9 1 . 0 0 . 0 9 9 . 9 1 0

7 3 . 2 3 . 6 4 4 2 . 2 5 274.63 999.64 1 5 3 . 7 5 1 . 0 1 . 1 4 0 . 2 3 3 S . 3 6 5

8 3 . 0 3 . 4 1 5 6 . 2 5 4 2 1 . 8 8 1 4 3 8 . 5 9 1 9 1 . 8 7 1 . 2 1 . 3 6 0 . 5 1 9 7 . 8 2 3

9 2.5 2.84 72.25 614.13 1744.12 2 0 5 . 1 9 1 . 1 1 . 2 5 0 . 5 4 1 1 0 . 8 0 3

10 1 . 4 1 . 5 9 9 0 . 2 5 8 5 7 . 3 8 1 3 6 3 . 2 3 1 4 3 . 5 0 0 . 7 0 . 8 0 0 . 0 9 1 2 . 9 1 5

6 6 8 2 . 5 8 9 4 3 . 4 3 2 6 0 . 0 3

(EAC)S = 6682 ._58 = 0.78, 70.8%, or 6.23 mm from the tegulum along the 943•4 3 Wing Span Line (WSL).

(EAC) = 260.03 _ o.027, 2.76%, or 0.24 mm in front of the Wing Span c 943.43 Line (WSL).

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