Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations
1969 Response of the adult European corn borer (Ostrinia nubilalis) to 0.3-15 micron radiation as indicated by respiration rate William Kenneth Turner Iowa State University
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TURNER, William Kenneth, 1933- RESPONSE OF THE ADULT EUROPEAN CORN BORER (OSTRIMA NUBILALIS) TO 0.3-15 MICRON RADIATION AS INDICATED BY RESPIRATION RATE.
Iowa State University, Ph.D., 1969 Engineering, agricultural
University Microfilms, Inc., Ann Arbor, Michigan RESPONSE OF THE ADULT EUROPEAN CORN BORER
(OSTRINIA NUBILALIS) TO 0.3-15 MICRON
RADIATION AS INDICATED BY RESPIRATION RATE
by
William Kenneth Turner
A Dissertation Submitted to the
Graduate Faculty in Partial Fulfillment of
The Requirements for the Degree of
DOCTOR OF PHILOSOPHY
Major Subject: Agricultural Engineering
Approved:
Signature was redacted for privacy.
Signature was redacted for privacy.
Head of Major Departmen
Signature was redacted for privacy.
raduate College
Iowa State University Of Science and Technology Ames, Iowa
1969 ii
TABLE OF CONTENTS
Page
INTRODUCTION 1
OBJECTIVES 4
ElEVIEW OF LITERATURE 7
European Corn Borer 7
Insect-Radiation Studies 8
Field studies 8 Laboratory studies, UV and visible 10 Electrcphysiclcgical studies 13 Laboratory studies, IR 14 X-ray, gamma ray, and radio-frequency studies 17
Environmental Variables 17
Biological Rhythms 21
Theories of Communication in Insects 24
Morphological considerations 25 Behavioral considerations 28 Environmental considerations 30
Observing Insect Activity in the Laboratory 32
Data Generation, Collection, and Analysis 35
PROCEDURE 37
Handling of the Insects 37
The Experimental System 41
Airflow, temperature, aad humidity control 41 Source of radiation 46 CO2 analysis 51 Data recording and processing 51
Test Routine 52
Analysis of Data 54 iii
Page
EQUIPMENT AND FACILITIES 62
Airflow, Temperature, and Humidity Control Apparatus 62
Radiation Apparatus 69
CO^ Analyzer 81
Data Acquisition System 87
Data Processing Equipment 90
RESULTS AND DISCUSSION 92
Response to UV and Visible Radiation 92
Response to IR Radiation 124
Critique of the Techniques 134
Experimental 134
Data collection and processing 136
Discussion 137
SUMMARY AND CONCLUSION 140
SELECTED REFERENCES 143
ACKNOWLEDGMENTS 158
APPENDIX A. IR RADIATION THEORY AND SAMPLE PROBLEM 159
APPENDIX B. DEVELOPMENT OF THE RESPIRATION MONITORING TECHNIQUE AND ITS APPLICATION TO SEVERAL TYPES OF EXPERIMENTS 171
APPENDIX C. REFERENCES BY SUBJECT 181 INTRODUCTION
Insects caused an estimated 15.6-billion dollars damage in the United
States in 1951. Losses of crops, stored products, domestic products, and
other commodities were estimated at 10.2-billion (138). For a single spe
cies, the European corn borer, an annual damage figure as high as 350-mil-
lion has been reported (159). As late as 1966, the estimate for this
insect was almost 156-million for the 14 major corn-producing states (160).
In bushels, the loss for 1966 amounted to approximately 2.95% of the total
national crop. Ic is not surprising chat extensive research is being con
ducted in an effort to control economic insects.
Insecticides have assumed a major role in the total area of insect
control. Skepticism, however, concerning the extensive use of some insec
ticides, because of their possible harmful effects on man and animal, is
encouraging the development and expanded use of other control measures.
Also, these chemicals may kill biological control agents of potential
pests, resulting in the rapid increase of these pests to economic levels.
Non-chemical control methods include those based upon physical, genetic, and biological principles. Improved cultural practices and the use of insect resistant varieties have already proven to be of great value.
Biological methods, including the propagation and distribution of parasites and natural predators, are receiving increasing attention. Dissemination of pathogenic organisms may prove to be of control value (138).
A relatively new development is the control of insects by mass release of sterilized specimens within a given geographical area. By releasing sterilized male screw-worm flies in numbers exceeding the natur:al popula 2
tion, the screw-worm has been eradicated in the southeast and southwest
United States (96). The potential of this method depends on the mating
habits of the insect, their geographical distribution, and other factors.
Considerable study has been given to the use of electromagnetic radia
tion to control insect populations. One application is the use of "light-
traps", usually employing an ultraviolet (UV) or visible source, to attract
and trap the insects. The primary weakness of this method is that the cap
ture does not usually constitute a significant portion of the population.
Light-traps have given an encouraging degree of control in a few cases, however (56).
The potential of electromagnetic radiation in insect control will probably be strongly influenced by the progress made in understanding their communication systems. Much of the research has involved the measurement of relative responses to various wavelengths of radiation. The basic nature of these responses and the biological mechanisms involved are usu ally not well understood. Several recent theories of insect communication may provide guidance in conducting research into new areas as well as giv ing better direction in the previously researched areas. Development of new radiation sources, such as lasers and solid state emitters, will also assist in expanding the research efforts.
There is a growing interest in the possible involvement of infrared
(IR) and microwave radiation in the communication of insects. Responses by certain species to IR at a wavelength of 337 microns have been reported
(107). The radiation for these studies was furnished by a laser.
Exploration into insect sensing of IR and microwave radiation presents a formidable challenge to researchers. One aspect of the challenge is the 3
range of wavslengths included. Compared to the one octave of the visible
region, the IR region covers 17 octaves and the microwave eight octaves.
Also, sources and detectors for many of the wavelengths in these regions are still in the developmental stages. 4
OBJECTIVES
The overall objectives of this study were to develop a technique for measuring responses of insects to a periodic radiation stimulus and to obtain a better understanding of the adult European corn borer's, Ostrinia nubilalis, (Hiibner) (Figure 1) responses to certain wavelengths of electro magnetic radiation. Specific objectives were as follows:
(1) To develop a procedure for measuring the responses of the adult
European corn borer to periodic radiation stimuli by using an
IR gas analyzer to continuously monitor respiration rate (COg
output).
(2) To develop convenient and compatible procedures for generating,
recording, and processing the insect response data.
(3) To determine the adult European corn borer's response to periodic,
narrow-band UV and visible radiation with peak wavelengths from
0.313 to 0.798 microns.
(4) To determine the adult European corn borer's response to periodic
wide-band IR.radiation with wavelengths from 1 to 15 microns. Figure 1. European corn borer adult (female)
/
ElEVIEW OF LITERATURE
Any insect response study must take into consideration the biological
properties of the insect and the physical properties of the environment.
Procedures for detecting and evaluating responses are necessary. For radia
tion studies, there is the need for presenting the radiation stimulus in a
manner to allow a maximum of response information. These aspects were con-
s ±dered in reviewing the literature.
European Corn Borer
Brindley and Dicke (21) have summarized the significant developments in European corn borer research up to 1963, including biological studies and research on the spread of the insect and control methods.
Information of importance to any response study with the corn borer c an be obtained from Sparks' (145) investigation of biotypes of populations of this insect in several midwestern states. The numbers of generations occurring in the different states are given as are the times of activity in trine field. Also given are the optimum mating conditions for laboratory rearing of corn borers.
Huber e_t al. (84) and later Stirrett (152) reported on extensive field s tudies, which included observations on flight, oviposition, and establish ment periods in the life cycle of the insect. The authors discuss climatic and other physical factors. Some of their findings will be reported in
Later sections.
Insects for experimental purposes are often reared on a continuous basis in the laboratory. Laboratory rearing of the European corn borer is ixa progress at the USDA Corn Borer Laboratory, Ankeny, Iowa (71, 108). s
Insect-Radiation Studies
Several references were reviewed that provide considerable information
in the area of insect-radiation research; these are given in the paragraphs
below. Information from the references will be included under appropriate sections of the review.
A brief but excellent review has been written by Nelson and Seubert
(121) on the use of electromagnetic and sonic energy for pest control.
Studies with radiation from gamma rays to radio frequencies were reviewed.
The bibliography contains 181 references.
Hollingsworth has summarized some of the more important field and lab oratory studies with UV and visible radiation, conducted through 1965 (80,
81). Proceedings of symposiua's dealing with the insects' relation or response to radiation are available and serve as useful reviews (56, 158).
O'Brien and Wolfe's (122) book, "Radiation, Radioactivity, and Insects", contains excellent discussions of the influence of radiation on insects.
The emphasis is on ionizing radiation, but a chapter on insects and light is Included.
Field scudies
Insect light-traps have become common, in field research and in a few cases have served to give a significant degree of protection against crop pests (56), Light-traps employ an attractance lamp and a means of captur ing or killing the insects (158). Lamps used in early traps were selected because of their output of visible radiation, hence the name light-trap.
The name continues to be used even when the radiation output is primarily
UV, as with blackllght traps. 9
Initial use of light-traps for trapping European corn borers started
around 1935 (77). (The terms European corn borer or corn borer refer to
the adult, unless otherwise stated.) From subsequent light-trap studies
with the corn borer, most researchers have found that lamps with a high
output in the near UV, from 320 to 365 mu, were most effective (9, 63, 157).
It appears Co be generally true that nocturnal insects show strongest
attraction to the near UV and to the blue end of the visible spectrum (48,
70, 94, 125, 137).
Calderwood (31) conducted a study to evaluate the field response of
European corn borers to traps having specially prepared reflective surfaces.
Instead of exposing tue lamp directly to the insects' view, the radiation
was reflected from a flat surface. Six different surface coatings were
used, of which four were fluorescent pigments and two were reflective
(aluminum and white enamel). The illumination, measured in foot-candles, was the same for each trap. A check trap, having a 15-watt blacklight lamp with two inches of the tube exposed, gave the same illumination. The order of effectiveness in trapping was as follows: sodium yellow, aluminum foil, signal green, white enamel, neon red, horizon blue, and the blacklight lamp.
These results are puzzling in light of the other cited work.
Hollingsworth £t al^. (82) have reported efforts to define optimum rela tionships between trap catches and lamp outputs for different species of insects. The results were reduced to simple mathematical equations relating relative catch to lamp output. Robinson and Robinson (136) spent consider able time observing Lepidoptera in flight in the vicinity of light-sources.
The authors reported that the insects did not appear to be "attracted" but upon coming within a certain range of the source were uncontrollably drawn tc-'ard it. By using coinbinations of power (lumens) and brightness 2 (lumens/cm ), they concluded that for any power the most efficient source
is that with the smallest radiating surface. Increasing the power resulted
in the attraction of more specimens of a particular species but did not
increase the number of species taken. An increase in surface brightness resulted in an increase of the species taken.
Polarized light has been incorporated into light trap studies. Kcvrov and Monchadskiy (97) concluded that lamps emitting polarized light were more effective in attracting certain Lepidoptera and Diptera, even with lower intensity, than similar lamps with no polarization. It is well known that honey bees utilize naturally polarized light in their navigation (161).
Recent studies have failed to show an influence of light polarization on certain nocturnal insects (105, 156).
Trap catches of certain species are markedly increased by placing vir gin female moths of the same species near the light trap (78). Catches of male tobacco hornworm, Manduca sexta. increased by an amount equal to the catch without females for each additional female up to ten. With the cab bage looper, Trichoplusia ni, females placed up to 40 feet from the trap had a positive influence on trap catch (76).
Laboratory studies. UV and visible
Most laboratory investigations have fallen into two categories, choice-chamber studies and electrophysiological studies. With the choice- chamber, the insects receive two or more different radiations simulta neously, and their position within the chamber is noted after prescribed time periods. Taylor and De ay (157) used a choice-chamber with various fluorescent lamps to test the corn borers' response to UV and visible radia
tion. Maximum response vas obtained with lamps having maximum output in
the UV at 320 and 380 mu.
When measuring response of insects to light, some obvious questions arise concerning the relationship between radiation intensity and degree of response. A customary procedure is to maintain constant intensity and dis
play response level as a function of wavelength, Weiss e_t (170, 171) concluded, however, from choice-chamber studies with Orthoptera, Coleoptera, and other insects, that of wavelength and intensity, the latter is more important in producing reactions. He pointed out that the difference in response to colors is not due to wavelength by itself but also to the dif ference in absorption of light by the primary photosensitive substance of the visual sense cells, which varies with wavelength (168). Examples were found, however, where different nerve fibers had different peaks of sensi tivity, which could suggest a form of color vision (167). Hecht and Pirenne
(75) emphasized the necessity of adjusting intensity to obtain the same physiological response, if meaningful comparisons are to be made.
Earp and Stanley (51) measured responses of tobacco ard tomato horn- worm, Manduca quinquemaculata. moths to eight narrow bands of UV and visi ble radiation with wavelengths ranging from 313 to 578 mu. A monochromator was used to furnish the radiation, and insect responses were observed with an IR telescope. Greater responses were found for the shorter wavelengths.
These findings were consistent with other work cited in the report.
Hollingsworth (80, 81) has compiled response curves for several insects that, in general, peak near 365 and 500 mu. The curves indicate weak response for wavelengths over 600 mu. In studies with cotton-insects. 12
he found that a linear increase in response resulted from a log increase in
intensity.
Weiss and associates (168, 169, 170) have conducted choice-chamber studies for more than 50 species using wavelengths from 365 to 720 mu.
Peak responses tended to center around 365 and 492 mu. Little response was realized at wavelengths over 590 mu and none at 720 mu. Most of these insects were diurnal Species. Stored grain insects have also shown peak responses at 365 and 500 mu (151).
Levengood and associates of the Willow Run Laboratories, University of
Michigan, have noted effects of combined stimuli. Using adult fall army- worms, Spodoptera frugiperda. the males showed a strong response to a com bination of female, moist moving air, and "blacklight". Response was increased with the addition of each stimulus (103). Other studies by this group have suggested that the antennae of adult corn eairworm, Hellothls zea. are involved in UV detection. Carbon dioxide output from moths with excised and intact antenna was measured while they were under the influence of UV. The respiration rate was less for the moths with antenna removed
(105).
Normal development of some insects is hindered under red light. Cod ling moths, Carpocapsa pomenélla. oviposited normally under light from the violet end of the spectrum but abnormally under red light (73). Retarded growth and early death occurred with the cockroach and milkweed bug,
Oncopeltua fasclatus. maintained In red light (7). 13
Electrophysiological studies
Employment of the electroretinogram (erg) to evaluate response of
insects to radiation has become common practice (117, 150, 166). An elec
trode is either inserted into the eye or given contact with the eye surface
through a suitable fluid. A second electrode is attached to the insect in
such a way as to furnish a reference for realizing a voltage potential dif
ference, between the electrodes, when a signal discharge occurs from some
part of the eye structure. An example of instrumentation and techniques for erg studies with insects has been described (150). No reports of elec
troretinogram studies with the European corn borer were found.
Generally, the same response peaks determined by choice-chamber meth ods are revealed by erg studies. Peaks at 550,500 and 360-380 mu were found for the tobacco hornworm moth (150). Several nocturnal moths showed peak response to radiation with a 550 mu wavelength (117). Best results were obtained from night experiments, even if several hours of dark adapta tion were allowed in the day experiments.
Walther (166) used the technique of varying intensity to obtain equal response from the cockroach. The studies were designed to evaluate effects of selective adaptation. The form of the retinal action potential varied with intensity, adaptation, wavelength, and portion of the eye irradiated.
He concluded that two receptor types were present that responded maximally to UV or green light. Violet adapting lowered sensitivity very little for any wavelength.
Callahan (35) has measured an action potential at the junction of the main antennal nerve and deutocerebrum of the brain of the cecropia moth,
Hyalophora cecropia, as the eye was irradiated with visible light. Response was also obtained using coherent red light from a ruby laser. An
action potential was obtained also from the scape dome sensor irradiated
with monochromatic yellow-green light.
An interesting aspect is suggested by visual threshold studies with
humans where the thresholds of the electrical signal and perception differ
(161). Perception may occur before the action potential (139). The same
may be true in insects.
Generally the compound eyes and ocelli constitute the photosensitive
parts of the insect. It has been shown with a species of aphid, however,
that light appears to act on receptors likely located in the dorsum of the
brain. The photoperiodic processes persisted even with the eyes covered
(122).
Laboratory studies, IR
Experimentation with insect response to IR radiation is relatively recent. No record of such studies on the corn borer has been located.
Sparks (147) used IR photography to observe the flight, feeding, and mating habits of corn borers in the laboratory. The insects did not show apparent disturbance by the IR source.
Referring again to the studies of Levengood and associates (101, 105,
107), a number of aspects of IR sensing have been explored. A Kanthal wire source, at temperatures of 100° and 120° C., failed to cause response with
the fall armyworm. Similarly, the 0.85 micron output of a gallium arsenide diode emitter, pulsed at frequencies from 1,200 to 12,000 Hz, caused no response by the fall armyworm or corn earworm adults (101). A significant finding has occurred with the Indian-meal moth, Plodia interpunctella. Ma les, subjected to narrow-band, far IR radiation, centered around 337 mi-crons, showed a positive response, i.e., they moved toward the end of the test chamber where the radiation was introduced (105, 107). The radiation
furnished by a cyanide gas laser operating with a pulse frequency of
I_3.5 Hz and ten microsecond pulse time. Low level UV and visible output
^zrom the laser was supposedly eliminated by using a black polyethylene fil ter. Weaker but significant response was also reported for fall armyworm and corn earworm (105).
Callahan and Cox (40) reported on several IR experiments. Radiation, h>earned through a silver chloride filter transmitting 3 to 30 microns, cr a-used the corn earworm to attempt flight and to display movements of the antennae and abdomen toward the filter within 60 seconds. The temperature of the filter was raised to 12° F. above ambient by the radiation. In other experiments with this insect, 100 adults were placed in a darkened room containing a 4-watt mercury-arc argon lamp whicl} had been completely covered with black electrical tape. In a period of several days, 52 of the moths Were trapped by "Stickum" placed on a horizontal surface around the
3_ainp. No moths were captured on a dummy check. An alternate experiment v^a.8 conducted employing an IR source in one end of a chamber and no source i-n the other end. Visual observations revealed 30 moths visited the source end while one visited the control end (34).
Among the most conclusive results from IR studies are those obtained fc>y Evans (58, 60). He examined sensory pits on Bupestidae, Melanophila acuminata, and proposed them to be IR detectors, based on their dimensions.
1tx±8 was prompted by the knowledge that this species flies to fires from
Xong distances. In laboratory experiments, response was obtained with vari- 16
ou s wavelengths from 2 to 6 microns, maximum response being at 3 microns.
Intensity was 6 x 10 ^ watts/cm^. Response occurred only when the radia
tion was focused on the pits or antennae. In o'.her tests, the beetles
would move randomly toward a heated nichrome wire a few degrees above
ambient temperature and probe with the antennae at the wire. This was sug
gested as response to convected heat received by sensors on the antennae.
Response to the low level monochromatic IR was rapid in contrast to the
slow reaction to the heated wire. Thus, long-range and short-range mechan
isms were suggested. Flashes of narrow-band IR of 1/2 to 1/300 second in
duration elicited a twitch of the antennae, a response which ceased if the
pit organs were painted with bronze paint. It was pointed out that forest
ers use IR detection devices to detect forest fires before other evidences appear.
Mosquitoes are known to be attracted to warm bodies (149). From one investigation, this response was attributed to convection heat since an infrared transmitting filter, placed between the mosquitoes and source, stopped the response (124). Callahan (33) claims a radiation response. He found Aedes aegypti to be attracted to IR at 1.05 microns which he stated is characteristic in the twilight sky luminescence and is reflected by human skin. This same article reports attraction of the Indian-meal moth to the aluminum end of a tube flooded with 1 to 2 micron IR radiation.
Mangum and Callahan (111) found that a modified mosquito trap, with an output of 0.8 to 2.8 microns, allowed trapping of Aedes aegypti In the lab oratory. To reduce the possibility of attraction by convected heat, the source was placed six feet away and the radiation reflected from an alumi num sheet at the top of the trap. Most mosquitoes were trapped within one 17
hour. Berry and Kunze (18) conducted investigations with stable flies,
Stomoxys calcitrans. and failed to obtain response to 115° and 100° F.
blackbody radiation. There was evidence of response to convected heat.
X-ray, gamma ray, and radio-frequency studies
Walker and Brindley (164) studied the effects of X-ray exposure on
male adults and pupae of the corn borer. Sterilized males survived well
and competed equally with untreated specimens. Raun et al. (131) irradia
ted the larvae of corn borer with gamma radiation. Pupation, moth emer
gence, and mating were nearly normal for doses as high as 5000 rad. Eggs
laid and egg hatch were most severely affected at 4000 and 5000 rad.
Brown (23, 25) found that planarians displayed orientational responses
to weak gamma radiation (a few times greater than that occurring naturally)
and artificially induced magnetic fields. Other influences such as moon
phase and time of year were involved.
Nelson and Seubert (121) have cited later work with radio frequencies
for controlling stored grain insects. Work by Nelson and associates showed
that control was possible for all developmental stages of several species
using a 39 MHz frequency (121).
Environmental Variables
A great deal of study has been made to relate the corn borer to its environment. This section, however, will serve only to suggest some of the many variables that are known or suspected to be important in insect experi mentation; it will not treat any particular variable thoroughly. Since the review is presented more by investigation than by variable, sub-headings will not be used. Because of the importance of rhythmic phenomena on the 18 activity patterns of insects, this subject will be covered in a separate section.
Using field data collected in Southern Ontario during the years 1921-
1936, Stirrett (152) presented a number of conclusions concerning the effects of climatic and other variables on the com borer. Some of his conclusions follow; All flight occurred between 56° and 87° F. with maxi mum at about 70°. Flight was more related to temperature than humidity, which did not seem to control time of flight. Most activity occurred from
1/2 hour to 4 1/2 hours after sunset with maximum activity at 1 1/2 hours after sunset. Moon phase, cloudiness, fog, or atmospheric pressure had no effect. Wind was not an influence if under 17 mph. Moths flew in light rains and were more active before thunderstorms.
Williams (174) has pointed out that it is difficult to determine weather effects because of the close correlation of a number of weather factors. This is emphasized by Everett et al. (61) and Sparks et (148) in reports of extensive studies, with the corn borer, conducted in three midwestern states over a 15-year period. Careful statistical analysis did reveal several correlations. Fall populations were positively correlated to nights with wind over 8 mph and amount of rainfall, during specific periods of time. Predator forms were correlated positively with accumula tive borer-degree days and negatively with temperatures below 58° F., again during specified times.
Jarvis and Brindlay (87) have stressed the Importance of daily tempera tures on the development of the corn borer. They present a method of pre dicting time of moth flight and oviposltion from temperature accumulations. 19
Sparks (147) found optimum mating conditions to be a 14-hour light,
10-hour dark cycle, daytime temperature-humidity conditions of 88° F. and
45-55% rh, and night conditions of 66° F. with 90-95% rh. The moths were given a 10% sugar solution, and 100% mating occurred.
Matteson and Decker (113) determined the temperatures resulting in minimum time spent in the egg, larvae, and pupae stages. They were, respectively, 80°, 90°, and 85°-90° F. Normal development occurred over ranges of 65°-80°, 60°-90°, and 60°-85° F., given in the same order. Nor mal development was defined as the range for which the temperature plotted against the reciprocal of duration in the stage was a straight line.
Light trap catches of corn borers have served as indicators of activ ity patterns. Greatest catches occur for temperatures over 70° F.; few are caught under 58° F. (77). The majority of flight activity occurs from dusk to 2 AM with maximum between 11 PM and 2 AM (62). Catches usually include more females than males (63, 77).
A few examples of effects of more subtle variables on insects will now be cited. Susskind (155) lists several variables including density of insects in the test cage, isolation of sexes, age, type of food, and possi ble differences in laboratory reared and wild moths.
Atmospheric pressure appears to have some influence on the emergence times and activities of some insects (173). Callahan (37) has reported that the corn earworm displays activity periods following diurnal pressure highs but is not influenced, apparently, by fast changes in pressure. The lack of correlation between pressure and activity in the field suggests this is not a critical factor in laboratory experiments with the corn borer
(152). Once again referring to the work of Levengood and group, experiments have revealed the importance of several subtle influences on insect behav ior. The female fall armyworm attracts more males if a flow of moist air moves across the female and toward the male (102). These same tests revealed the importance of using young moths and conducting the experiments at night when normal, nocturnal activity occurs. The importance of avoid ing certain odors became apparent when moths showed a strong negative response to stagnant water and even to the container after several attempts at cleaning (103). Response to vibration was observed when evaluating
Indian-meal moth response to a blacklight lamp placed behind a black poly- ethlene film. With the light source in contact with the film, response was noted but ceased when the source was not in direct contact with the film
(106). Lastly, a positional bias of almond moths. Cadra cautella. was attributed to strong electric fields around the laser used in the response studies. Repositioning of the insect chamber eliminated the bias (107).
Maw (114) reports where a chance situation revealed that parasitic
Hymenoptera Insects were discouraged from entering a trap carrying a static charge. A rotating net, forming part of the trap, brushed a corn leaf and caused a 40-volt/cm potential from net to ground. This evidence was veri fied by catches in traps given a static charge by friction.
Investigation of insect response to light changes necessarily involves light and dark adaptation processes. Required times for these processes have been suggested for various Insects (47, 117, 166). Most researchers agree that both types of adaptation are fairly complete within an hour.
Post and. Goldsmith (128) working with the moth, Gallerla mellonella. sepa rated dark adaptation into two phases, the first lasting about 1 1/2 to 2 21
minutes, before eye pigment movement started, and the second being the pig
ment migration process, typically taking 20 to 30 minutes and progressively
lowering the sensitivity threshold. During light adaptation, almost cota- 3 -1 -2 -4 plete pigment migration was caused by 5 x 10 ergs sec cm (5 x 10 -2 watts cm ) at 500 mu. The first phase of light adaptation was rapid,
being complete in a few seconds. Response varied only slightly after this
first phase of adaptation. A similar phenomena was found by Bernhard and
Ottoson (16, 17) in studying dark adaptation of nocturnal and diurnal
Lepidoptera, including Cerapteryx graminis. The adaptation process pro
ceeded in two phases. The second phase appeared to be associated with pig
ment movement which began after approximately five minutes of darkness.
There is a relationship between pigment migration and activity (46,
53, 79). Collins (46) stated that the iris-pigment had to be in the pro
cess of moving for the codling moth to be physiologically responsive.
Speed of migration and degree of activity were related to quality and quan
tity of light. Not only does pigment migration depend on illumination lev els and changes but follows a rhythmic pattern of change with a 24-hour
period, even in constant darkness (117, 122). Edwards (53) pointed out a degree of independence between the migration and activity, concluding that
the pigment change is secondary in effect to the general circadian activity rhythm.
Biological Rhythms
An investigator of insect response to almost any stimulus is forced to consider the biological rhythms displayed by the insect of interest. For example, an insect that is responsive to visible radiation at night might 22
not respond during the day, even after several hours of dark adaptation.
The procedure of rephasing nocturnal insects to daytime activity by an
appropriate history of photoperiod control must be employed with reserva
tions; all cyclic phenomena may not rephase (104, 105).
A large amount of research has been devoted to biological rhythms dur ing the last two decades. An excellent collection of knowledge was brought together at the 1960 Cold Spring Harbor Symposium on Biological Clocks (45)-
A later collection is available in the published proceedings of a school on circadian clocks held at the Feldafing Summer School, Holland, in 1964 (5).
Bunning's (28) "The Physiological Clock" is still another valuable informa tion source. Beck (10), who has conducted extensive research on diapause in the European corn borer, has written a book entitled "Insect Photoperi- odism".
The work of Beck and associates, concerning diapause in the (11, 12,
13) corn borer, is of interest to the present study since the complete pro gram of rearing and handling of the insect influences the responsiveness of the test specimens. For the corn borer, photoperiod appears to be the dom inant factor in diapause control under ordinary conditions.
A few examples will illustrate some of the important aspects of bio logical rhythms. Minis and Pittendrigh (120) report that the pink bollworm moth, Pectinophora gossypiella. develops a circadian rhythm of hatching under certain circumstances. This rhythm derives from circadian oscilla tions in each egg, which can be initiated or made synchronous by steps or pulses of light or temperature, but only if these signals are administered after the midpoint of embryogenesis. 23
Twenty-four hour periods of larval activity on foliage, adult emer
gence, and flight of lepidopterous defoliators have been recorded automat
ically, by various means (55). The rhythms were found to be adapted to the
seasonal environments normally experienced by the insects, and activity was
influenced by changes in light and temperature. Some activities were par
ticularly associated with sunrise while others were more related to sunset.
Adkisson (3) has reported that diapause in the pink bollworm is usu
ally not greatly influenced by short breaks in light or dark periods. But
he also described cases where a one-second flash of light at the proper
tiras prevented diapause. In addition to effects from light-dark cycles, changes in light level have been shown to modify the circadian rhythm (110).
An important consideration is that constant conditions, so diligently sought for in the laboratory, may be detrimental to the organism by break ing down the circadian system. It appears that constant darkness is not detrimental to many insects, but constant light is (126).
Southeast Asian fireflies display an interesting phenomena. Males tend to flash at regular intervals, and, if in "sight" of each other, their flashing is brought into synchronization. Whole treefulls will ignite and lapse back into darkness at approximately two times per second, for hours
(175).
Drosophila (fruit fly) has been a favorite test insect for rhythm stu dies. Pittendrigh (127) proposed temperature insensitive, inherited bio logical clocks, based on studies with this insect. Temperature has an influence on circadian periods but not nearly to the extent it affects met abolic activity. Certain rhythmic performances in the Drosophila were improved by circadian periodicity in the temperature regime, in conjunction 24 with the light regime (126). Recently, phase setting of circadian rhythms in the insect has been accomplished by a temperature square-wave pattern.
Rhythm phase shifts were produced by application of steps or pulses of tem perature change (179).
Rensing (133) has reported evidence of circadian rhythms in Drosophila as indicated by their oxygen consumption. Blmodal fluctuations were mea sured showing a wide maximum in the evening and a steeper one in the morn ing. This bimodal fluctuation persisted for two or three days under pre sumed constant conditions.
Shorey and Gaston (143) have studied several Noctuidae for their responsiveness to sex pheromones at various times during a 24-hour period.
A cyclic rhythm of responsiveness was observed, and this could be entrained to abnormal light-dark cycles.
Brown (24) has reported a number of other phenomena related to cir cadian rhythms. With various test animals, including 5ome insects, cir cadian rhythms have been shown to be influenced by weak magnetic fields, very weak electrostatic fields, and weak gamma fields. Evidence usually consisted of modified patterns of orientation and travel direction, with the degree of modification dependent on such factors as solar and lunar phases and time of the year.
Theories of Communication in Insects
Among the factors suggesting that Insects may possess modes of commun ication not presently recognized are the following:
(1) The efficiency with which they locate their host and locate each
other for mating purposes. 25
(2) Morphological structures on their body that are not defined as to
purpose and have the appearance of sensory organs (64).
(3) Phenomena in their environment that would be useful in communica
tion or survival activity provided they could sense them (31, 32).
(4) Various flight and other phenomena that are difficult to explain
based on present knowledge.
Morphological considerations
Theories on insect communication involving radiation, other than visi
ble and UV, have been proposed by a few researchers. Grant (69) has sug
gested that certain insect antennal sensory pits are waveguides rather than auditory sensors, based on structural dimensions and properties such as
dielectric constant. Measurements, taken from available scale drawings of various sensory type structures, revealed transverse dimensions ranging from 5 to 40 microns. As waveguides, these structures would serve best as transmitters or resonators for IR radiation having approximately these wave lengths.
Grant (69) illustrates the inadequacy of recognized functions to explain activity by reference to the parasitic wasp which locates prey through wood, apparently by stidulating the wood surface with the antennae.
Grant acknowledged that an earlier observer had suggested IR detection since certain IR frequencies penetrate dry wood.
Schneider (64) has described nine types of sensillae found on antennae.
The functions were given where known. Duane and Tyler (49) found that hairs on the antennae of the cecropia moth tend to vary in length, in incre ments, from 40 to 80 microns, suggesting a tuned antenna array. 26
Field and laboratory studies with Meianophila have been cited.
Because of this insect's apparent ability to perceive IR radiation, a study
was made its sense organs (59). Revealed were spherical, cuticular
structures, approximately 15 microns in diameter, with a central cavity
connected to the distal process of a nerve cell. Wax glands secreted wax
strands over the organ; a dust protection function was suggested. No mech
anism of wavelength selectivity was proposed from these studies.
A rather elaborate theory of insect communication has been proposed by
Callahan (32, 35, 36). Involved in the theory are concepts of detection of radiation of Che microwave to the ionizing frequencies, emission and modu lation of some of these frequencies, insect body parts with thermoelectric properties, maser action connected with insect and plant scent molecules, and patterns of environmental phenomena. The ommatidia of the eye are described as mosaic, fiber optic devices, the ocelli as immersed optics, and various spines and pits on the antenna and elsewhere as waveguides or resonators. According to Callahan, these descriptions are encouraged by the following morphological and physiological considerations:
(1) Pigment cells move to alternate locations depending on the qual
ity and quantity of radiation striking the eye. This is suggested
as a process changing a UV-visible, daytime detector to an IR,
nighttime detector. Thickness of the pigment layer and relative
positions of pigment, reflective elements, and nerve endings are
suitable for transfer and detection of the entering radiation of
the proposed wavelengths.
(2) The corneal lens of the eye las transmission windows in the IR
bands 1-2.5, 3-6, and 7-14 microns. 27
(3) Waxy substances are present which polarize and depolarize with
changes in heat and electrical fields.
(4) The ocelli appear to have a sensing element beneath a relatively
large radiation collecting lens.
(5) Sensillae on the antennae have transverse and longitudinal dimen
sions of magnitudes suiting them for reception and transmission
of IR and microwave frequencies. Dielectric constant, wall
thicknesses, and degree of taper are near that called for by
electromagnetic wave propagation and detection theory.
A recent development in the theory that insect spines serve as radia tion detectors comes from the work of Susskind and associates (155) at the
University of California. They have constructed two models of a typical spine of the corn earworm moth, closely reproducing dielectric properties and configuration, and scaling size from micron to centimeter magnitudes.
The models were based on excellent micrographs obtained with scanning and standard electron microscopes. One model was solid and the other hollow.
Using a circular waveguide as a feed structure, signals were fed to the 9 model spines at microwave frequencies of 4 and 10 GHz (IGHz » 10 Hz), the desi-gn center frequency, and 2.5 times this frequency. Improvement in directivity and gain was moderately well satisfied at 4 GHz but not at
10 GHz. The results suggest that the spine does receive electromagnetic energy in the IR at an optimum wavelength of 4.35 microns.
Susskind's report includes the relevant thought that insects may not be attracted to IR for the same reasons that humans are not attracted to vi8i.ble sources. Rather, the interest is with particular objects illumina-, ted by the source, such as another moth or a plant host. A composite 28
theory dealing with the role of insect sensors and giving an integrated
picture of behavior is presented in the reference.
Behavioral considerations
Corn borers appear to be proficient in their mating abilities. In
Boone County, Iowa, in 1951, a population estimated at 19 pairs per acre accomplished near 100 percent mating as evidenced by spermatophore counts^.
This proficiency is not expected when considering the lack of long distance responsiveness to the female sex pheromone by the males (95), the lazy nature of their flight, and the poor visual acquity characteristic of insects. Another interesting ability is that of locating the healthier or more highly fertilized plants within a field (29).
Mazokhin-Porshniakov (118) made observations of nocturnal insects in the vicinity of light sources and reported a number of flight patterns including straight, zigzag, and chaotic. His suggestion was that insects seek "open" territory characterized by an abundance of short-wave radiation including UV. Hence, a UV lamp would naturally attract Insects. The theory that insects approach a light on a logarithmic spiral path was not supported by his observations. Robinson (135) and Robinson and Robinson
(136) state that the insects do not appear to be attracted but suggest a
"dazzle" zone; if the insects pass through this zone, they are drawn, uncontrollably, toward the light.
Callahan (38) proposes that apparent confusion among the Insects is caused by changes occurring in the eye (processes of adaptation to light or
^T. A. Brindley, Ames, Iowa. Based on data.'from field-sGudies. Pri vate communication. 1969. dark conditions) and conflict between the functions of the eye due to the laap emitting both IR and visible or UV radiation. This supposes that the eye is a sensor of both visible and IR radiation, the particular mode depending on the illumination level being experienced by the insect.
The responsiveness of many nocturnal insects to UV has been documented.
Response curves, showing relative response for various wavelengths, are often similar in shape to the absorption curve for chemical rhodopsin or visual purple, which is abundant in animals that see well at night (81).
Human vision is restricted in the UV partly because the lens of the eye filters out these wavelengths. When this lens is absent, as in the akpak- tic eye, vision is enhanced in the violet and UV.
Smith e^ (150) reported that electrophysiological investigations of the nervous system of tobacco hornworm moths revealed that electrical signals from a nerve leading to the flight muscles were influenced by UV light delivered to the eye. He suggested a possible association between this response and the insects' strong response to blacklight lamps in the field.
Reichardt (132) reported on optomotor reaction studies with the fly,
Musca, aimed at determining the number of quanta of radiation necessary for detection by this insect. The fly was mounted on a torque detecting device and presented with various programs of low-level light. Results suggested that a single quantum of light. If absorbed, sets a finite probability for the elicitation of a primary physiological event which in turn may cause other events.
References reporting response to infrared by several species of insects have been cited. Other behavior factors suggested as indicating 30
the feasibility of IR sensing capabilities are the rise in body temperature
upon wingbeating or vibratory action, the modulation of the emitted grey-
body radiation through wingbeating, reflecting of IR by the wings and other
body parts, at certain wavelengths, and the stability of the antennae in
flight, allowing proper positioning for detection purposes (36, 39).
Several researchers have measured temperatures of active moths (1, 64,
74), It was reported that the sphinx moth, Calerio lineata, by muscular
activity and flight, maintains a nearly constant thoracic temperature,
regardless of ambient temperatures between certain limits. Upon heating with IR lamps, the insect tcck flight when the thoracic temperature reached
37.7° C., which is near that maintained in flight (1, 74). A thoracic tem
perature of 19° C. above ambient has been measured (34).
Environmental considerations
Environmental factors play an important part in the insect communica tion theories of Callahan (36) and others (155). The moths are picture^ in an environment where spatial pockets of optimum temperature and moisture exist and where a variety of radiation signals, generated by the atmosphere, objects, plants, and insects themselves, make up a communications complex
(32, 37, 38).
Plants have been shown to fluoresce in the UV, visible and IR (4, 115,
154). Also, IR reflectances of plant leaves have been measured (178). The reflectance is generally low for wavelengths between 2 and 14 microns, not exceeding 0.05 for wavelengths greater than 3 microns. Values are greater between 2 and 3 microns; a fairly sharp maximum at 2.2 was noted for a mature bean leaf. Studies in progress at the present time are yielding interesting
results. Levengood and associates (107) have discovered that certain
insects respond to plants located behind polyethylene windows. Fall army-
worm females responded positively to a corn plant placed behind a clear
polyethylene window, in a large test cage. When a tomato plant was used,
the plant had to be in contact with the window and even then produced a weak response from the insects. Males of this species failed to show response to the corn plant until it was illuminated with a blackiight fluo rescent lamp; a strong response was then obtained. The lamp was not in the moth's line-of-sight. A weaker but significant response occurred with black polyethylene replacing the clear. Earlier tests had shown no response by these insects to zhe light-source positioned behind the black polyethylene.
Due to the previously found response to sub-millimeter radiation (337 microns) and the transmission of these wavelengths by the polyethylene, it was suggested that these wavelengths might be involved. In connection with this research, thermographic scans were made of a tomato plant. These scans showed higher emission in the 8 to 14 micron region for the plant as compared to the background. This contrast between plant and background was much sharper when the plant was pre-exposed to sunlight as compared to cloudy conditions.
Mazokhin-Porshniakov (116) measured UV reflectance from butterfly wings and concluded thiô factor to be important in identification. It has been shown that the UV content at night varies considerably (15). Callahan
(36) photographed the adult corn earworm with 1 micron IR and found it gave a bright image, indicating good reflectance. 32
of the conmunication capabilities of insects have been attributed,
by ma.^xrx-y researchers, to odor sensing. Laithwaite (99) questioned this on
the g oiinds that useful odor gradients would be destroyed by irregular wind
pattet^Er"ris. The analogy of a smoke concentration gradient was given. He
propo^s ed radiation sensing in the infrared. Kettlewell (93) objected to
this «contention and defended the odor sensing aspects.
^ "lie gaseous composition of the environment may be important in insect
activ:m_ ty. Riddiford and Williams (134) concluded that volatile material
from c—>ak leaves, perceived by sensory receptors on the antennae of the
polypi -m. -c rnOth, AnthcTSc^ ^ol^^hêmi^, i.5 cSScHtial fox rcLêaSë of the
femal^^ sex pheromones. Carestia and Savage (41) found that several species
of mo^= ^uitoes are attracted tc CO^ levels above ambient. This was shown by
using "bottled CO^ or dry ice to produce CO^ at rates from 250 to 2000
cc/mir*. -
Observing Insect Activity in the Laboratory
E*.s.Trk conditions during the experiments with IR or UV radiation pre clude -visual observation. Also, for experiments that extend over a long
period- of time, say 24 hours, an accurate, automatic response monitoring systerr*. is needed. Many "uch systems have been devised; some are reviewed here.
B- ^2cause researchers have found a general lack of response by insects to the far-red portion of the visible spectrum, it has been supposed that near I lEt could be used for observation without influencing the activity.
Sparks (146) photographed nocturnal activity of the corn borer using IR illumi:na. tzion and appropriate film. The insects did not appear to be dis- 33
Curbed by the radiation. Others have used an IR telescope to view response
activity directly (51). In still another application, the interruption of
an IR beam, by flying insects, resulted in a recorded signal. The number
of beam interruptions was taken as proportional to activity (27).
A simple capacity sensing device has been used to detect the movements
of a cockroach over a period of months. Aluminum foil capacitor plates
were situated under and around the activity chamber (140). Edwards (52)
took advantage of the static charge on insects and employed a probe that
picked up a signal from the flying insect. To obtain a better understand
ing of the reason for charge on insects, he brought test specimens in con
tact with various substrates and measured thé resulting charge. Sign of
the charge depended on the substrate (54). Jones e_t al. (90) used sensi
tive microphones to study circadian flight of mosquitoes.
During activity, the metabolic rate of insects increases many times over that of the inactive state, as much as 1300 times for the honey bee
(138). This suggests respiration as a useful criteria of response. Several methods have been devised to study metabolism and patterns of respiration.
Among the methods are those involving CO^ and 0^ diaferometers (130), the
Warburg apparatus (44), electronic respirometers (65), and gas chromatog raphy (42, 43).
One of the applications of the Warburg apparatus was to evaluate effects of radio-frequency electric fields on the yellow mealworm, Tenebrio molitor (91). Hamilton (72) measured the CO^ output of individual locust by passing air through a tube containing the insect and then through an IR
COg analyzer. The tube and insect were submerged in a constant temperature bath. 34
Application of CO^ analysis to plant photosynthesis studies has been more extensive than it has for insect studies. Of interest are the tech niques developed for closed and open circuit systems. With the closed sys tem, the COg is maintained in a gas-tight circuit; the analyzer monitors the accumulated level (22, 109).
For experiments to measure CO^ exchange and transpiration in whole plants, a method has been developed for obtaining air of known CO^ content by first removing the CO^ and then adding a known amount (162). A system, for determining CO^ exchange in diseased radish tissue, was designed for automatic operation, requiring little attention (19). Several of the above references describe methods of controlling temperature, humidity, and com position of the test gas.
An important consideration with both the open and closed system, but especially the closed system, is che diffusion of CO^ through the walls of tubing and components (26, 100). It has been shown that diffusion of CO^ through teflon and polyethylene is slow (123). For a 0.0005-inch thick 2 film, the CO^ diffusion was 5 cc/m /min. This amount may be significant where CO^ levels change very slowly in a closed system.
Brown (26) presents an excellent discussion of sources of errors involved in gas analysis with the IR analyzer and offers several sugges tions for preventing or reducing these errors. Stow (153) has shown that other gases in the mixture, pressure design characteristics, and other variables may result in systematic errors. Brown (27) has given a techni cal treatment of the principles of IR gas analysis including mathematical descriptions and weaknesses Inherent in the method. 35
Data Generation, Collection, and Analysis
For many insect response studies, particularly if the evoked response
is weak, sensitive analytical techniques will be needed to retrieve the
information from the response record. A logical approach is to offer the stimulus as many times and to as many insects as is feasible in a given time period and then add the evoked signals. By offering the stimulus periodically, the resulting record will lend itself to several analytical approaches including regression, correlation, and spectral techniques.
Linear regression methods are more familiar to the average scientist than correlation and spectral methods. This review will be devoted to the latter two techniques.
Mercer (119) has discussed correlation and spectral techniques in relati-on to analysis of biological records containing periodic phenomena obscured by random fluctuations. In addition, he discussed electronic techniques. Winget (176) has made an application to simultaneous records.
Parameters of deep body temperature, heart rate, and locomotor activity, in the ctxicken, were recorded and the records subjected to periodogram and correLation analysis to reveal the rhythms.
Correlation and spectral methods have been used extensively for analy sis of electroencephalograms (eeg). Walter (165) described a procedure and gave a. concise mathematical treatment. Barlow (8) has developed a tech nique for on-line analysis of electroencephalograms. A high speed auto matic curve reader reconverted the trace to electrical form which was sent to a Exequency analyzer or a digital correlator if auto and cross-correlo- grams -were desired. Two simultaneously recorded tracings» from two eeg leads, were used to evaluate the subjects' responses to photic-stimulation. 36
Much of the development of spectral methods has been prompted by prob
lems in the field of communications. Blackman and Tukey (20) have contri
buted substantially to this development. This reference contains a mathe matical treatment of the subject and a thorough glossary of terms.
Methods of analysis of economic time series may suggest approaches to biological data analysis. Certain similarities exist between these series and periodic stimulus-insect response records. Periodic stimuli are pres ent in the work week, pay periods, financial policies, seasons, etc. (68,
88). Also, there are random activities and trends in the economic record as in the insect activity record. 37
PROCEDURE
In conducting the study, the various processes included insect hand
ling, presentation of the radiation stimuli, measurement of the CO^ pro duced by the insects, and recording and analyzing of the data. Laboratory reared European corn borer adults were subjected to periodic radiation stimuli, and the response of the insects was measured by continuous moni toring and recording of their CO^ production. Radiation was presented to the insects for five minutes every 30 minutes over a period of about 23 hours. Recording of the data on punch-paper tape allowed data processing, including computer analysis, with a minimum of hand operations and calcula tions.
The major phase of the study consisted of 60 tests involving 18 dif ferent wavelength bands of radiation. A test with a particular waveband was replicated three times, which is referred to as a treatment. Six tests were conducted using no radiation stimulus. Of the radiation treatments, three were narrow-band UV, 11 were narrow-band visible, and four were wide band IR. A single test required a 24-hour period. Figure 2 shows the por tion of the electromagnetic spectrum involved in the experiment (B) and its position in the total spectrum (A).
Handling of the Insects
The European corn borers used in this study were obtained from the
United States Department of Agriculture, European Com Borer Research Lab oratory, Ankeny, Iowa. Continuous laboratory rearing of the com borer is in progress there. Because the method of handling earlier generations may Figure 2. Electromagnetic spectrum (A) showing bands of energies, frequencies, and wavelengths and an expanded representation (B) of the portion of the spectrum involved in the insect- response study Wavelength (X), microns 15 1 0 1 .5 0.75 0.7 0.6 0.5 0.4 0 Far Middle Near -a Near 0 IR IR IR 2 0 m UV blue > green >
Portion of spectrum used in the insect - response study
Gamma Rays X - Rays ijj Ultraviolet >0 Visible Infared
Radio Waves
-13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 Energy of the quantum (E) , 1 .24 x 10"^ electron volts
7 8 9 10 11 12 13 14 15 16 17 18 19 20 Frequency (v), 3 x lO"^ cps
17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 0 -1 -2 Wavelength (A) , 10" Angstrom Units 40
influence the responsiveness of the present generation of insects, a cycle
of the continuous rearing process is presented next.
First-instar larvae are placed in small glass vials containing a care
fully prepared food medium, and the vials are closed with cotton plugs.
The larvae are incubated at 80° F. and 75% rh under continuous fluorescent
light for 21 days. After 21 days, the cotton plugs are removed and the
vials are transferred to oviposition cages, which are placed in another
incubator room. Here a light-dark cycle is maintained with 16 hours of
light followed by eight hours of darkness. During the light phase, the
temperature is 80" F., and rh is held at approximately 75%. Moths emerge and leave the vials, mating occurs, and eggs are layed on wax paper disks situated within the oviposition cage. The eggs are gathered each morning and transferred to an incubator having the same conditions as that used for first-instar larvae. Hatching occurs in four days, larvae are placed in vials, and the cycle repeated.
To obtain moths for the study, the following procedure was carried out. Vials of the first-instar larvae were delivered to Ames, via automo bile, twice weekly. They were placed in a small room where temperature and rh were maintained at 80 + 1° F. and 85 + 5%. Two 15-watt daylight fluores cent lamps were used for the light phase of a 17-hour light and 7-hour dark cycle. The lights were turned on at 7 AM (all times will be Central Stan dard) and off at 12 midnight. Approximately two days after pupation, the pupae were transferred to small plastic jelly cups fitted with waxed paper lids. In a few days, moths emerged and were available for the experiments.
Under the influence of the light regime, a circadian rhythm was estab lished in the insects that finally resulted in practically all moths ecerg- 41
irxg during Che dark phase. Only moths emerging the night before and ap^pearing to be in good physical condition were used in the daily tests.
The Experimental System
Brief descriptions of the components and processes of the experimental system will be given here. Detailed descriptions are included in the
Eqtiipment and Facilities section. Reference to Figure 3, which shows the organization and components of the entire system, will aid in following the de scriptions.
Airflow, temperature, and humidity control
In order to measure the CO^ output of the insects as they were sub jected to various stimuli, it was necessary to know the CO^ content of the aixT before it entered the insect chamber (Figure 4). This was made simple by removing all CO^ from the incoming air. Compressed air was passed through stages of pressure regulation, filtration, and metering, through a potassium hydroxide column, to remove the COg, and finally through a slightly heated water column before entering the insect test chamber. Con trolled heating of the water column allowed control of the rh of the air.
The conditioned air passed through the insect test chamber, picking up
CO^ produced by the insects through respiration. From the insect chamber, the air passed through a filter, to remove insect scales, before entering the COg analyzer. The air from the analyzer was exhausted to the atmo- sptaere. All the components were Interconnected with 3/16-inch ID tygon or teflon tubing.
The water column, used to achieve the desired relative humidity of the air , was maintained at 76 + 1/4° F. Air passing through the column was Figure 3. Flow diagram of insect response study processes 43
INPUT OUTPUT I I Compressed Air UL Corn Bcrer Particle Filter Loborotory Liquid Troo Ankeny, lowo 90 psi U. First instar Pressure AO V larvae, from Regulator the rearing M 5 psi process, ore placed in small Drying gloss viols Column Tronsformotions Spectral Analysis Odor Eliminator Regression Anrtlyti;
F low-meter Computer
To Ames Mog. Tope Particle Filter Permanent
Larvae Pressure Mog. Tope, Regulator arorv 1 psi 11 Paper Tope Adults Needle Volve Reader
Radiation 4 KOH Co' umn Sources Paper Tope CO2 Reipoved
H2O Column Data Acquisition TT Sydwm Punch Ghgmbcr I I 3r CZatisk^niL ] Coupler CO2 Gas Anqlyxtr. IDVM Flow Procesi Air Bubble Strip-chart Radiation Electrical Flow îfalÈL. R>fiflfd«r Mechanicol Exilioust Figure 4. Insect test chamber 45
w » > brought essentially to this temperature and approached saturation. Then,
as the slowly moving air passed through the interconnecting tubing and into
the insect chamber, its temperature was raised to approximately 80° F.
This resulted in a rh of the air in the insect chamber of approximately 85%.
Temperature in the insect chamber was maintained at 80 + 1/4° F. by
placing it in a well insulated environment box and supplying heated air via
an external heat source and ducting. A temperature control circuit sensed
and continuously controlled the heat delivered to the box.
Source of radiation
A Perkin-Elmer Model 81, single-pass, prism monochromator was used in
combination with a modified source platform and three different radiation
sources to furnish wavelengths from 0.313 to 15 microns. For the UV and
visible tests, the monochromator was used in a normal manner providing nar- row-band radiation with the bandwidth depending on the wavelength setting
and the monochromator slit-width adjustment.
For the IR tests, the monochromator optics were not involved except for a flat mirror which was positioned to reflect the entering radiation
directly toward the insects. Wide-band interference filters, placed imme
diately in front of the insect chamber, permitted only the desired wave
length band to reach the insects. No interference-type filter was avail able for the 1-3 micron waveband; a combination of filters was used for
these tests. Information on transmission characteristics of the filters is
given in Table 1.
Three different radiation sources were used. Advantage was taken of
the principal spectral emission lines from a mercury-vapor lamp, to supply 47
Table 1. Transmission data for filters used in IR tests
7o Transmission Microns 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Filter
RG-10 99 98 14 (5% at 0,7*)
UG-8 45 99 32 (5% at 0.9*)
L-02130-8B 00 00 93 87 (5% at 2.31*)
L-05080-9A 00 00 00 00 01 87 87 (57, at 5.13*)
L-08220-9A (5% at 8.20*) 00 89 89 91 88 89 80 65
Irtran II 40 63 67 70 72 73 73 73 73 72 70 68 63 48 00
Cut-off points for the IR interference filters were approximately as follows L-02130-8B 6 microns L-05080-9A 10 microns L-08220-9A 15 microns
* Lower cut-off points, in microns. the UV and part of the visible wavebands. These bands centered around wave lengths of 0.313, 0.334, 0.365, 0.405, 0.436, 0.546, and 0.578 microns.
The lamp voltage was maintained at 120 volts, and the desired radiation intensity was obtained by adjustment of the monochromator slit-width. For the UV tests, black glass filters were placed immediately in front of the insect chamber to reduce the stray radiation reaching the insects.
The remainder of the 11 visible wavebands were furnished by an iodine- quartz tungsten-filament lamp. Proper intensity was obtained through adjustment of the lamp voltage and monochromator slit-width. Second-order interference filters were available for seven visible wavebands and served
1I 48
to reduce stray radiation. Half widths of these filters ranged from 10 to
20 mu. Table 2 contains source and monochromator slit-width data and iden
tifies the filters used for all tests. The windows used on the insect cham
ber are also identified. A Nernst glower source provided the four wide
bands of IR radiation. Adjustments of the Nernst glower current and mono
chromator slit-width gave the desired intensity.
Radiation intensity was maintained at a constant level for the UY and visible tests. If the intensity for the wide-band, IR tests had been the same as for the UV and visible, the energy per unit wavelength would have been much less for the IR. Therefore, the intensity for the IR tests was the maximum permitted by the source and was about 20 times that of the UV and visible tests. Because the output of the IR source was low for the 8.5 to 15 micron range, the intensity for this waveband was about half the intensity of the other three wavebands.
To permit adjustment of the radiation intensity level, a diagonal mir ror was positioned to direct the radiation to the detector. The optical window and filters to be used in the test were placed in the radiation path.
Chopping of the radiation beam, near the source, resulted in an AC signal from the detector. This signal was received and amplified by a Princeton
Applied Research, HR-8, lock-in amplifier, and the intensity was adjusted by the means appropriate for t^e particular source.
Once the radiation Intensity level was established, the filters were positioned for the test, and the optical window was fitted to the chamber containing the insects. The chamber was placed in the environment box, and the diagonal mirror rotated to allow the radiation to enter the chamber. Table 2. Source and filter information for UV, visible, and IR tests
Slit- Insect Wavelength Voltage or width Filter chamber Code (microns) Source current (mm) identifIcation window
I 0.313 Mercury-vapor 120v 1.000 F-Sl UG-LI suprasll, quartz 2 0.334 Mercury-vapor 120v 1.700 F-S UG-11 A suprasil, quartz 3 0.365 Mercury-vapor 120v 1.400 F-S UG-ll A suprasil, quartz 4 0.405 Mercury-vapor 120v 0,375 None A suprasil, quartz 5 0.436 Mercury-vapor 120v 0.200 None Class 6 0.475 Iodine-quartz 70v 0.700 None Glass 7 0.514 Iodine-quartz 65v 1.000 B&L^ 42-47-56 Glass 8 0.546 Mercury-vapor 120v 0.170 None Glass 9 0.578 Mercury-vapor 120v 0.400 B&L 44-73-00-580 Glass 10 0.605 Iodine-quartz 55v 1.000 B&L 42-47-58 Glass 11 0.660 Iodine-quartz 55v 0.700 B&L 42-47-59 Glass 12 0.700 Iodine-quartz 70v 0.860 E&L 44-78-00-700 Glass 13 0.752 Iodine-quartz 60v 0.700 F-S RG 10 Glass B&L 44-78-00-750 14 0.798 Iodine-quartz 60v 0.600 F-S RG 10 Glass B&L 44-78-00-800 15 1-3 Nernst glower 400 ma 1.257 F-S UG 8 (2) Glass F-S RG 10 (2) 16 2.5-6 Nernst glower 300 ma 1.150 OCL^ L-02130-8B Irtran II 17 5.3-10 Nernst glower 470 ma 1.430 OCL L-05080-9A K Irtran 11 18 8.5-15 Nernst glower 500 ma 2.000 CCL L-08220-9A K Irtran II
Fish-Schurman Corp.
Bausch & Lomb, Inc.
Amersil, Inc.
Eastman Kodak, Co.
Optical Coating Laboratory, Inc. Because the air in the insect chamber was maintained at 80° F. and the
laboratory room was at approximately 67° F., the space within the monochro
mator housing was heated to prevent condensation on the insect chamber win
dow. The monochromator was equipped with heaters, and its temperature was
maintained at 80° F. A short plexiglas tube connected the monochromator
and environment box.
Radiation entering the insect chamber was periodic, after being inter
rupted by a chopper blade operating near the radiation source. The chop
ping frequency was maintained at approximately 17 Hz. This was the average wingbeat frequency of several corn borers whose individual frequencies were determined with a strobe light. An aluminum foil disk, fastened to the rear of the insect chamber, served to reflect and distribute the chopped radiation throughout the chamber.
Quantitative determinations of intensity were not afforded by the thermister detector and lock-in amplifier combination. An ISCO SR spectro- radiometer was used to obtain quantitative measurements. Because of the construction of this instrument, it was not possible to locate the large radiation collection window at the position corresponding to the insect's location. A remote detector probe, furnished with the instrument, made the measurements possible. Because of the low sensitivity of the instrument, when using the probe, the probe detector head had to be located at the exit slits of the monochromator. With intensity at the exit slits known, inten sity at the insects' location was determined by geometrical considerations. "6 2 Intensity levels were found to be approximately 6 x 10 watts/cm for the
UV and visible tests and 120 x 10 ^ watts/cm^ for the IR tests. 51
CO^ analysis
A CO^ analyzer, Beckman model IR 215, was used to measure the absolute
value of the CO^ content of air from the insect chamber, i.e., parts per
million by volume. A calibration curve furnished with the instrument gave
the COg content at any specific meter deflection. This instrument was
relatively free of influence by other component gases normally found in air,
although moisture did have an effect. A baseline for moist air flow was
established, and this constant value was later subtracted from the test
readings. The accuracy of this procedure was tested by injecting known
quantities of CO^ into the system, at the insect chamber location, and com
paring the injected amount with that determined from the recorder trace and
calibration curve. These values were very close, within 5% for all cases.
Data recording and processing
A continuous record of the analyzer output was obtained with a Brown,
model 15, strip-chart recorder. In addition, a Vidar 5202 D-DAS data
acquisition system (DAS) was employed, which consisted of an integrating
digital voltmeter (IDVM), a system coupler, and a tape punch assembly. The
IDVM received the analog signal from the CO^ analyzer, integrated this sig
nal over 166 2/3 milliseconds, and delivered the averaged value to the
punch, via the coupler, in 1248 BCD code. The coupler was programmed to
deliver a four-digit number to the punch. Only numerical information was
punched; algebraic sign and decimal location were not since they remained constant.
The gas analyzer millivolt output was recorded once each minute using a cam timer to actuate the DAS signal reading and punching process. Visual 52
an^B-Hysis of several recorder traces revealed that a recording rate of one
pen— minute was satisfactory to sufficiently define the CO^ output. Three rep» ILications of each test were performed before the punched tape was ren-3.cDved for further processing.
Information on the punch-paper tape was transferred to a magnetic tape wit In a punch tape reader and an incremental, digital, magnetic tape rec order. This transfer process allowed a check on the number of recorded vaL u.eSy giving assurance that a value was recorded each minute of the exper- ime TIC. Once the transfer process was terminated and the magnetic tape was rentoved from the recorder, no additional records could be added to this tap'^^. Therefore, another transfer was made on an IBM 360 computer, and eve:arxtually all records were included on a single magnetic tape.
Due to the large difference in day and night activity of the insects, the records were divided into two equal length records of ten hours each, witZrk. Che first period extending from 12:06 PM to 10:06 PM and the second from 10:06 PM to 8:06 AM.
Test Routine
A single test required a 24-hour period. The test routine can best be ill*j.s trated by listing the steps in order of occurrence.
(1) 8:15 AM The CO^ analyzer was calibrated. Then the air supply
line was connected to the analyzer. Several minutes were allowed
for the COg-free, moist air baseline to come to a steady-state
reading. The meter pointer was set at 3% of full-scale deflec
tion, using the zero adjustment control, to account for the
deflection caused by the moisture in the air. 53
(2) 8:20 AM The radiation source was adjusted to the desired wave
length and intensity level. Chopping rate of the radiation was
maintained at 17 Hz during adjustment and during the experiment.
Any required source change was made at this time.
(3) 8:30 AM Two male and two female moths were placed in the clean,
glass test chamber. A 1-inch square of fiberglas screen material
was dipped in distilled water and placed in the test chamber,
affording a free-water supply for the insects. The appropriate
optical window was fitted to the chamber using neoprene o-rings
and secured in place with a plexiglas frame and connecting bolts.
(4) 8:35 AM Air flow rate was checked with a flow meter and any
necessary adjustments made to obtain a reading of 50 + 0.5 cc/min.
(5) 8:45 AM The insect chamber was placed in the environment-box and
connected into the air line. The lid of the environment box was
fitted in place. A period of insect adjustment was allowed
before the DAS was placed in operation.
(6) 12:06 PM Recording of the CO^ analyzer output signal, by the DAS,
was initiated by manually starting a 1-minute cam timer. The DAS
was energized continuously with the exception of the punch which
was operated only during the 20 hours of the test. Timing of the
punch operation was precise to assure time synchronization
between the radiation periods and recording of the CO^ output.
(7) 8:06 AM Data recording was terminated by manually disconnecting
the 1-minute cam timer. Thus, for the 20-hour test, 1200 CO^
measurements were recorded. 5A
(8) 8:10 AM The insect chamber was disconnected from the air line
and removed from the environment box. The air line was then
reconnected for the analyzer calibration. Die insects were
removed from the chamber and weighed on a Mettler type H6T elec
tronic balance. Female moths were kept for examination to deter
mine if mating had occurred. Radiation intensity was rechecked.
If intensity varied more than 10% from the original setting, the
test was repeated.
This test routine was repeated every 24 hours. A treatment of three replications were run on successive days. After the three tests with a specific waveband of radiation, the paper tape containing the coded data was removed and marked with an identification code. A record log was main tained which included date, experiment code, wavelength band, monochromator and radiation detection amplifier settings, filter types, radiation source power supply settings, CO^ analyzer calibration settings, and exact times for each hand operation.
Analysis of Data •
If the flight activity of the insects was strongly influenced by the periodic radiation stimulus, this was evident in their COg output. Not all stimuli exercised a strong influence, and visual observation of the COg record did not always allow certainty about the existence of an influence.
Therefore, statistical methods were sought that would establish the influ ence with a certain level of confidence.
Since the only activity of interest to this study was that related to the radiation stimulus, it was desirable to find a statistical method to 55 emphasize this activity and deemphasize all others. One other obvious periodic influence was that related to the circadian rhythm; activity was greatest at night. This means that the 20-hour record of CO^ output prob ably did not possess the characteristic of stationarity, i.e., the statis tical properties of the record changed with time. Another influence was the degree of response which varied widely from one stimulus period to another. These are just two of the complicating factors involved in the statistical analysis of the data.
During discussions of this work with statisticians, it was suggested that a computer program devised for statistical analysis of economic time series be considered; portions of the program were used for the analyses.
Some of its important features are presented next.
The economic time series program was designed to do simple transforma tions, arithmetic operations, spectral analysis, regression analysis, and plotting. Because the program was modular in nature, new functions or other statistical analyses could be easily added without changing the existing program. The program permitted large quantities of data to be processed; as many as 999 files, each having 1800 observations. Various tasks were implemented by use of simple parameter cards, allowing use of the program by those with no previous computer experience. Several program segments were permanently stored on disks, and desired segments were brought into use by appropriate parameter cards. Considerable flexibility existed within each program segment.
An indication of the nature and versatility of this program is given in the following listing of selected segments and their functions. (1) Reader: to get a new series on disk so that the other program
segments could be used. Data could be read from disk, cards, or
magnetic tape.
(2) Input/output: to print files in legible form, to plot the obser
vations in the files, to punch the file out on cards for use in
other programs, and to perform several other functions.
(3) Regression: to do a regression analysis on the standard regres
sion model complete with t and F values. Up to 98 independent
variables could be handled.
(4) Arithmetic unit: to do arithmetic operations on files. Opera
tions such as selection of desired segments of data, transforma
tions, data generation, and rearrangement of data were performed.
(5) Spectral unit: to do a straight or cross-spectral analysis and
plot the results.
Before performing statistical analyses, it uas necessary to relate the millivolt signal of the COg analyzer to the CO^ production by the insects.
From the gas analyzer calibration curve, values of ppm CO^ and millivolt output were obtained for several points and punched on computer cards. A third order regression equation was determined by using a polynomial regres sion program (85). CO^ values given by this equation, compared to the calibration curve values, were within 1% over the entire range of the curve.
A value for ppm CO^ for any value of millivolt output was given by 2 3 * ^ *1 +*2? ^ + a^y where
X " ppm COg
y = millivolt output 57
a, = intercept J. a- _ . = regression coefficients
To obtain the quantity of CO^ produced by one insect in one hour, consider
w = f(x,c,s,r) where
w = cc CO2/insect/hr.
c = constant correction factor for moisture in the air
8 = COg analyzer signal amplification
r = air flow rate
Then, for three replications with a single wavelength band of radiation, involving 12 insects,
-1 -1 (r cc min )(x.-c+x--c+x -c)(60 min hr ) w(cc hr insect ) = c (10 )(12 insects)
Thus, w represents the average CO^ output per hour per insect based on the outputs of 12 insects.
The value of c was determined by calibrating the analyzer for a zero meter deflection when dry nitrogen passed through the instrument and then noting the meter deflection when the moist air passed through the instru ment. This value was expressed as ppm CO^ and was considered a constant for all tests. Transformation of the raw data, using the above equation, was accomplished with the arithmetic section of the computer program.
These transformed data were then available, in computer storage, for analy sis.
Regression techniques were used to analyze the data. In regression analysis, it is well known that using the method of least-squares in the presence of autocorrelated errors leads to inefficient estimates of the 58
parameters in the regression model (89). By autocorrelated errors or dis
turbances is meant the correlation of the error at time t with earlier
errors, say time t-1.
The Durbin-Watson d statistic was used to test for the presence of
autocorrelated disturbances. Let z^(t=l,...n) denote the residuals from an
estimated least-squares regression. The test statistic is defined as
The Durbin-Watson procedure to test for positive autocorrelation is as
follows: Compute d; if d is less than d^, reject the hypothesis of random
disturbances in favor of that of positive autocorrelation; if d is greater
than or equal to d^ and less than or equal to d^, the test is inconclusive.
The lower and upper confidence limits, d^ and d^, depend on the number of observations, n, and the number of independent variables in the regression model. Durbin and Watson (50) calculated values of d^ and d^ for up to 100 observations and one to five independent variables.
For the analyses of the insect response data, n was 600, and there were 35 independent variables. Thus, an approximate test for autocorrela tion was obtained from the relationship
d = 2(l-r) where r is the estimated correlation between residuals with one time lag
(67). The degrees of freedom used in testing the significance of r were the same as for the regression sum of squares in the model. The correla tion coefficient, r, for 35 degrees of freedom, at the 5% level of signifi cance. is 0.325. By the approximate relationship given above
d = 2(l-r) = 1.350
Thus, for a d greater than 1.350, the hypothesis of random disturbances was not rejected.
For the regression analysis, a regression model was required. The steps leading to the model are presented next. In the following discussion,
Y denotes the observations in the series made up of the 600 w values.
Estimates for the mean response function, Y, are defined to be
19 Y Y, = 2.-—^ for i = 1,2,...,30. j-0
This series of 30 observations was repeated 20 times in order to obtain a series of identical length with the original series of w values. Regres sing the Y values on the estimates for the Y function resulted in a very low value of the J statistic. This meant that the residuals from the sim ple regression model were not independent and so either the model was inade quate or the model was adequate but autocorrelation was present in the residuals.
Observation of the insect CO^ output traces strongly Indicated time trends and also suggested the possibility of time trend - mean response interactions. Several regression analyses were performed, with each suc cessive analysis being based on a regression model having higher degree terms. A term was eventually Included to account for possible autocorre- lated disturbances; the degree of the postulated autoregresslve structure for the errors was Increased for successive analyses. It was found that 60
one of Che CO^ records, on which the preliminary analyses were made,
required a model having time trend and interaction terms up through cubic
and a third-order autoregressive model for the errors. Thus, the following
regression model was chosen:
Y = u + a. + B,(a t) + B_(a t^) + B (a.t^) + B t + B^t^ + B,t^ + v. L 111 Z1 J1 O L
't " Pft-l + 'I't-l + P3^t-3 + S where t denotes time and t = i + 30j, i = 1,2,...,30; j = 0,1,...,19 and where
u = mean of the
= deviation of Y^ from the mean of Y^
B^ = regression coefficients, k = 1,2,...,6 and e^ are assumed to be independently and identically distributed with mean zero and constant variance.
The estimation procedure involved a two-step regression analysis. In — — 2 3 2 3 the first step, Y^ was regressed on Y^, Y^t, Y^t , Y^t , t, t , and t .
Residuals generated from this regression were then used to estimate the coefficients Pj^, p^, and p^ in the autoregression model. All variables in the regression model were transformed using the estimated autoregressive parameters denoted by q^, q^, and q^. In a general notation, the transfor mation was the following;
\ - qiZc.i - Qg^t-Z " = 4,5,...,600.
The transformation reduced the number of observations on each variable by three. "k In the second step, the transformed Y^ values (Y^ ) were regressed on * the transformed independent variables. The Y^ values were regressed first on all the independent variables to obtain the regression sum of squares, 2 3 denoted RSS (full model), and second on the time variables t, t , and t to
obtain the regression sum of squares, denoted by RSS (reduced model).
To test the significance of the mean response function, the sum of 2 3 squares attributable to t, t , and t was subtracted from the sum of 2 3 ~ 3"" squares due to t, t , t , Y^., tY,, t Y ., and t Y^ . The F test for testing
the hypothesis that treatment effects are null was constructed as
RSS (full model) - RSS (reduced model) p32 ^ 32 561 Residual SS (full model) 561
Of the 32 degrees of freedom for regression, 29 came from the 30 means and 2™ one each came from tY\, t Y^, and t Y^. The 561 degrees of freedom for error were obtained as 596 (degrees of freedom for total SS when 597 obser vations were used) minus 35 (degrees of freedom for RSS (full model)).
One of the objectives of the study was to compare response levels for the various radiation stimuli. A simple comparison was possible by consid ering the maximum variation in the mean response function, Y^. Because the level of CO^ output varied considerably between radiation treatments, the difference was divided by the minimum Yi as a normalizing measure. Thus, the response index, RI, was defined as
Y (max) - Y (min) RI = — 2 Y^(min) 62
EQUIPMENT AND FACILITIES
This section includes a discussion of the experimental system and per
tinent information on the major components of the system. A portion of the system, including the radiation equipment, insect environment box, and CO^ analyzer, is shown in Figure 5. In Figure 6, the environmental box and monochromator covers have been removed.
Airflow, Temperature, and Humidity Control Apparatus
Several components were involved in regulating and conditioning the flow of air that passed through the insect chamber and to the CO^ analyzer.
These components are shown in Figure 7 and are lettered in the order of their placement in the system.
Incoming air was furnished by a central compressed-air storage facil ity with pressure maintained at approximately 90 psi. After leaving the central facility line, the air passed through a combination particle filter and water trap, then through a Fisher type 67 pressure regulator where pres sure was reduced to 5 psi. Following the regulator were a CaSO^ drying column and an activated charcoal column for removing odors. The next com ponent was a dual-float flowmeter which gave a rough indication of the flow- rate. The air then passed through a Matheson model 71 pressure regulator, which brought the pressure to 1 psi, and a Nupro B-25 needle valve which was adjusted to obtain the desired air flow-rate.
The low pressure air then passed through an 800 liter potassium hydrox ide (KOH) column, with a concentration of 360 grams of KOH per liter of water, to remove CO^ from the air. After the KOH column and Immediately preceding the insect chamber was an 800 liter water column which was main- Figure 5. General view of the experimental system ready for operation. The envircnssntal box is in the center, the zcncchrczatcr at left center, and the CO^ analyzer at lower right
Figure 6. General view of the experimental system with environmental box and coverings removed to show arrangement of essential components J including the insect chamber 64 Figure 7. Components of the system for regulating and conditioning the air supply for the insects A. Combination particle filter and liquid trap B. Pressure regulator C. Drying column D. Odor removal column E. Flowmeter F, Particle filter G. Pressure regulator H. Needle valve I. KOH column (CO^ removal) J. H2O column (humidity control) K. Insect chamber L. Particle filter
67 tained at a specified temperature by means of heat tape. Passage of air through the water column resulted in delivery of the CO^-free air to the insect chamber at the desired rh. Because the laboratory room in which the tests were conducted was maintained at a fairly constant temperature, the water column temperature was controlled by simply adjusting a variac to supply the required voltage to the heat tape. To minimize short-term fluc tuations in the temperature of the column, it was wrapped with insulation material. The KOH and water columns were designed so that air entering the columns at the base had to pass through a 1-inch diameter, coarse, fritted- glass filter. These filters served to break the air into many small bubbles assuring proper CO^ removal and humidification.
With the insect chamber located in an 80° F. environment and the water column at 75° F., the rh of the air in the chamber vas calculated to be approximately 85%. Two checks were made to verify the rh estimate figure.
Wet and dry thermocouples were placed in the insect chamber, the wet one being inserted into the inlet port to assure a flow of air over its surface.
For the second check, a Honeywell rh indicator, Model W661Â, was employed.
The remote sensing probe was inserted into the insect chamber. Several measurements by each method indicated a rh between 80 and 90%.
To prevent insect scales from entering the analyzer, a 24-cc flask with a ground-glass stopper was filled with spun pyrex glass and inserted in the air line just ahead of the analyzer. After the air passed through the analyzer, it was exhausted to the atmosphere. The analyzer and spun glass filter offered negligible resistance to the air flow, making the pres sure in the insect chamber essentially atmospheric. 68
Airflow, for all tests, was maintained at 50 + .5 cc/min. The airflow
rate was checked before and after each test by connecting a 25-cc bubble
flowmeter to the exhaust port of the analyzer and timing the travel of a
bubble over this volume. Bubbles were obtained by using a Nuclear Products
"Snoop" solution. This flow meter was made from a 25-cc pipette by forming a flange on one end for fitting a rubber squeeze bulb and connecting a short length of glass tubing at a point 1-inch below the graduations to serve as tne inlet port.
The insect chamber was constructed from a glass jar and was approxi-
had a ground-glass finish for sealing an optical window with o-rings.
Inlet and outlet ports allowed passage of air through the chamber. For ease of connection into the air system, ground-glass ball and socket joints were attached to the ports using tygon tubing sleeves. Other interconnec tions between the components of the air-flow system were made with 3/16 inch I.D. tygon or teflon tubing.
Temperature of the laboratory room in which the tests were conducted was maintained at 68 + 1° F. An 80° F. environment for the insect test chamber was achieved by enclosing the chamber in a heated, 1-foot cube, insulated box, of wood construction. Heated air was delivered to this box via a 4-inch diameter flexible tube which connected with a separate box containing a 600-watt, 220-volt cone heater and a Rotron whisper fan to circulate the heated air. A temperature control circuit, employing a ther- mister sensor, held the air temperature surrounding the insect chamber at
80 + 1/4° F. The sensor was situated in the warm air inlet port of the environment box. Voltage applied to the cone heater was 120 volts during 69 the heating cycle. The circuit diagram for the temperature control unit is shown in Figure 8.
Laboratory room cooling was accomplished with two evaporator units located inside the room. Because of the sensitivity of corn borers to noise and vibration changes, the evaporator fans were operated continuously.
This also afforded mixing of the air and improved room temperature control.
A microphone and tape recorder were used to monitor noise level changes at the insect chamber location. Noise level was audible but fairly constant.
Acoustical tile was used to line the environment box, and the insect cham ber was supported on a polyfoam pad to reduce noise and vibration. Portions of the polyfoam pad were cut away to allow a fixed and stable support for the chamber, assuring its location in the same position for each test.
Temperatures at several points in the system, including the insect environmental box, water column, and laboratory room, were recorded every 8 minutes with a Brown, model 15, multi-point recorder and appropriate thermo couples.
Radiation Apparatus
A Perkin-Elmer, model 83, single-pass, prism-type monochromator was used to furnish the radiation (Figure 9). The source and source optics platform was modified to allow use of available sources. Sources included a Nernst glower for the 1 to 15 micron IR wavelengths and either a General
Electric H 100 A-4/T, 100-watt mercury-vapor lamp or a Sylvanla 475-watt iodine-quartz lamp, type FAL, for the UV and visible wavelengths. Cooling was required for the latter two sources; this was afforded by a 100-cfm squirrel-cage fan mounted above the source location. Changes from one Figure 8. Insect environmental box temperature controller circuit DC POWER SUPPLY SENSOR AND DC AMPLIFIER , 10 A 12 VDC o- ~"lNE-2 1 117 VAC ® Neon] IGA45J, i'X ' Amplified 1.0 «Sensing 200V IN41^ Signal 100 mf Output 2.2K 2N3391 20V 5W 2N33W^ -)k— 2.5K 680 ^ WW 12V < 470
J 1.5K nihil + 12 VDC /777J7? TRIGGER POWER SECTOR
117 VAC 117 VAC Trigger Signal Trigger Signa 'Output Input
200V Sensing Signal Load Input lOOOW CI 0681
rrttn Figure 9. Radiation equipment showing monochrornator and associated components. A. Chopper blade speed control unit B. Chopper blade C. Reference signal circuit voltage supply D. Reference signal circuit E. Lock-in amplifier for indicating radiation intensity level F. Bias circuit and preamplifier for radiation detector G. Nernst glower H. Iodine-quartz source I. Movable mirror
Mercury vapor source and power supply for the nernst glower are not shown 73 74
source to another required only the repositioning of a single, flat mirror.
This mirror was equipped with spherical locating feet which fitted into a
triangular pattern of three V slots assuring consistent positioning for all
tests.
To better utilize the output of the iodine-quartz lamp, it was mounted
in front of a half-section of a cylindrical metal sleeve that was lined with aluminum foil to act as a reflector. A piece of quartz tubing was inserted over this assembly to reduce the infrared energy reaching the monochromator and to better direct the flow of cooling air. The maximum voltage applied to the lamp was 70 volts, resulting in long lamp life.
Wavelengths from 0.475 to 0.798 microns were supplied by this source.
The principal spectral lines of the mercury-vapor lamp yielded all the desired UV wavelengths and some of the visible wavelengths. Because the energy of the different spectral lines varied, it was necessary to vary the bandwidth of the output radiation to obtain uniform intensity levels. Vari ations in bandwidth were obtained by adjustment of the monochromator slit- width.
A Nernst glower with its current control circuitry and power supply was standard equipment in the Perkin-Elmer model 13 spectrometer, from which the model 83 monochromator was taken. Current in a Nernst filament must be continuously controlled. A red sensitive photodeteccor tube, loca ted near the glower, monitored the radiation output and furnished a feed back signal to the control circuit.
No air-circulation cooling of the Nernst source was used because air currents cause erratic temperature changes in the filament and result in erratic output and shortened life. Current through the element was kept at 75 or below 0.5 amps. Shielding of the source and photodetector area from extraneous light was necessary since the control circuit was influenced by such light. Radiation output of the Nernst glower is similar to that from a blackbody at the same temperature. However, emissivity of the source varies with wavelength. Approximate outputs of the glower at two current settings are shown in Figure 10. Descriptions of this source are found in texts on infrared (112).
The radiation was periodically interrupted with an 11-inch diameter rotating disk located at the entrance to the monochromator and driven by an
Electro-Craft series E-500, motor and speed control system. This system consisted of a motor-generator with a feedback amplifier for speed adjust ment and control. With adjustable speed, it was possible to set the chop ping frequency to that of the insects' wingbeat frequency.
A Barnes S-IOO-S thermister detector was used in combination with a
Princeton Applied Research HR-8 lock-in amplifier to establish radiation intensity levels. The detector was located at the focal point of an ellip soidal mirror which collected the radiation to be measured. Two thermister flakes were present in the detector. One flake received the incident radi ation while the other was shielded from incoming radiation and was influ enced only by the ambient temperature of the detector. The active flake was blackened to better absorb radiation, resulting in a fairly flat responsivity over a range of wavelengths from 0.3 to 35 microns.
Responsivity of the detector used in the study was 480 volts per watt of incident radiation. Intermittent radiation, falling on the active ther mister flake, caused heating and cooling of the flake with a corresponding Figure 10. Nernst glower output at two different currents. IR inter ference filter transmission ranges are indicated by the arrows Output , RMS Microvolts Full Scole o o O
w CO
OI
f < 2- n CO a g: O
to OI
OI 78
change in its electrical resistance. The active and inactive flakes formed
part of the detector bias circuit (Figure 11).
For the thermister type detector, highest detectivity occurs at chop
ping frequencies near 10 Hz. Detectivity drops only 2 db as the chopping
frequency increases from 10 to 20 Hz. Thus, chopping at 17 Hz (insects'
wingbeat frequency) allowed satisfactory performance of the detector.
The signal lead from the detector was connected to a high impedance
Princeton Applied Research Type A preamplifier. The biasing circuit and
preamplifier were located within a few inches of the detector, and the
assembly was shielded with a metal cover. Interconnections between the
detector and preamplifier were of solid, uninsulated, tinned, copper wire
to prevent static electrical charges and microphonics under conditions of
vibration. A capacitor was inserted in the preamplifier lead to eliminate
problems with DC voltages. A remote cable assembly connected the preampli
fier to the amplifier.
Operation of the lock-in amplifier required a reference signal of the
same frequency as the signal from the detector, i.e., the frequency at
which the radiation was chopped. For this signal, an electrical circuit
(Figure 12) was constructed which included a low voltage incandescent lamp
and a 1P41 photodetector tube. The lamp and tube were located on opposite
sides of the chopper blade so that the tube received intermittant light. A
satisfactory reference signal, approximating a square-wave, resulted from
the circuit.
A fan and shutter arrangement was used to facilitate the presentation
of radiation to the Insects for a 5-minute period, every 30 minutes. The
fin was turned on at the proper time by a Selectro Corporation model Figure 11. Bolometer detector circuit
Figure 12. Circuit used to provide reference signal for lock-in amplifier 80
157.5 V ^ Active n~+ Thermistor ! I ir Prs — j { Amp I 157.5V — Compensating + 3 Thermistor
+ Î250VDC
4.7 W
$4.7M 0.5 mfd & 12AU7A
omfd II © PAR HR-8 Ref. Input
OVDC 81
92-1066 snap-action contact programmer with a 1-rph synchronous drive motor.
Actuators were positioned on the drum of the programmer and trimmed with a
razor blade to give the desired time program with + 2 seconds.
Air from the fan displaced a pivoted aluminum flag to which was
attached a 3-inch lever arm. A string connected an aluminum shutter to the
lever arm. The shutter was pivoted and positioned so that with the fan off, the radiation was prevented from entering the monochromator. With the fan on, the shutter moved to allow the radiation to enter the monochromator.
This arrangement is shown in Figure 5.
CO^ Analyzer
Analysis of the CO^ content of the air from the insect chamber was accomplished with a Beckman IR-215 infrared gas analyzer. This instrument, with the cover and housing removed, is shown in Figure 13.
The principle of operation of the analyzer was that IR energy at spe cific wavelengths is absorbed by COg. Figure 14, which shows a functional diagram of the analysis section, will assist in understanding the operation of the analyzer. IR beams from two similar sources were directed through cylindrical gas cells having a highly reflective gold plating on the inside and fitted with quartz windows on each end. A chopper blade alternately interrupted and passed the IR beams ten times per second. One of the gas cells was designated the reference cell and was permanently filled with nitrogen. The other cell was fitted with inlet and outlet ports to allow the air under analysis to be passed through it. .
A double compartment detector, filled with COg, was attached to the cells at the end opposite the IR sources. Each compartment received radia- ^igure 13. Infrared CO2 analyzer with cover and housing removed to show analysis and detection sections 83 84
tioa passing through its respective cell. Differential absorption of IR
energy in the two detector compartments depended on the absorption that had
occurred in the gas cells. The nitrogen in the reference cell absorbed a
negligible amount of IR energy. Thus, the energy absorbed in the reference
side of the detector was constant while that absorbed in the test side
depended on the CO^ content of the air passing through the sample cell.
Differential heating occurred in the detector compartments resulting in
differential expansion of the gases and movement of a thin diaphragm sepa
rating the compartments.
This diaphragm constituted one plate of a capacitor in an electronic
tank circuit. As the diaphragm vibrated at 10 Hz, the resonant frequency
of the tank circuit changed slightly about a center frequency of approxi
mately 10 MHz. This changing resonant frequency modulated a 10 MHz carrier signal through transformer coupling (Figure 15). Efficiency of the trans former and, hence, amplitude of the 10 MHz carrier decreased as the tank resonant frequency moved further away from the 10 MHz value.
Rectification and filtering of the modulated carrier signal isolated
the 10 Hz signal. This signal was amplified, rectified, and filtered to obtain the DC signal for operating the integral meter and a recorder. Thus,
the degree of distention of the diaphragm was indicated by the DC voltage output of the analyzer, and this was related to the CO^ content of the air under analysis.
By potentiometric adjustment, the output signal of the analyzer was adjusted to cause full-scale deflection of a 10 mv recorder when air con taining 215 ppm COg was passed through the sample cell. A 1% recorder Figure 14. Functional diagram of analysi# section of CO^ analyzer
Figure 15. Modulation section of CO^ analyzer 86
Chopper Motor
Reference I R Sample IR Source Source
m t) — Sample In V 5 u« 0) £ 0) R- fh Detector Oscillator Unit
To Amplifier/Control Section
To Amplifier/Control H Section
|DeTe^o7| 0) E
c o 10 MHz I I Oscillator I I
Slug Adjustment 87
deflection indicated approximately a 2 ppm change in CO^ content; a change
of this size was easily detected.
Before conducting the insect response experiments, the calibration
curve furnished with the analyzer was verified. By using various mixtures
of nitrogen and air with a known CO^ content, the calibration curve was shown to be reliable. As mentioned before, CO^ quantities calculated from the recorder trace compared well with known quantities injected in the sys tem at the location of the insect chamber.
Data Acquisition System
To facilitate computer processing of the raw data without becoming involved in intermediate hand operations, a data acquisition system (DAS) was employed (Figure 16). The system used was a Vidar D-DAS which included a Vidar 520 integrating digital voltmeter (IDVM), Vidar 653-02 system coup ler, and Vidar 662 tape punch and power supply. The tape perforator was a
Tally Corporation model P120.
The IDVM received the DC signal from the gas analyzer and integrated the signal over a selected time period. Upon the proper command, the mil livolt input was integrated for 166 2/3 milliseconds, and the coded infor mation became available at the output terminals. The integrating and read out process was initiated by an external switch closure.
The system coupler served as an interconnecting and formatting device providing compatibility between the IDVM and the punch. In operation, the coupler converted parallel BCD data words to 8-level IBM characters for recording by the punch. Word-length and character arrangement were fixed by a format plug which was electrically wired for the desired format. Figure 16. Data acquisition system and other data recording equipment 89 Finally, the IBM characters were punched into the one-inch wide paper tape
by the tape perforator.
Because of the noise associated with the operation of the punch, the
DAS was placed in an insulated cabinet. Heat dissipation was assured by
mounting two 100-cfm squirrel cage fans to the cabinet and providing an air
intake port at the end of the cabinet opposite the fans. As an additional
safety feature, the DAS power supply was connected in series with a thermo
stat, adjusted to switch the power off if the temperature in the cabinet
went above 100° F.
Data Processing Equipment
The coded, numerical information on paper tape was transferred to
9-track magnetic tape via an intermediate step. A punch-tape to magnetic
tape converter, consisting of a teletype paper punch-tape reader, accom
panying circuitry, and a Precision Instrument's PI 1200 incremental, digi
tal, 7-track, magnetic tape recorder, was used to transfer the information
to a 1,200 foot reel of magnetic tape. Once this transfer process was ter
minated and the magnetic tape dismounted from the recorder, additional
records could not be added at a later time. Ihus, it was necessary to make
a second transfer. This involved transfer of the digital Information to a
2,400 foot reel of 9-track magnetic tape, a process carried out on an IBM
360 computer, using a utility program.
Eventually all experimental records were stored on a 9-track tape and were available for computer processing. Mathematical processing and sta
tistical analyses of this data were accomplished with an IBM 360 computer. 91
Plotting was accomplished with a Cal-rotii, Digital Incremental Plotter using a Simplotter graphing routine. RESULTS AND DISCUSSION
A technique was developed for measuring responses of the adult Euro
pean corn borer to periodic radiation stimuli. The technique included con tinuous monitoring and recording of the insect's respiration rate (CO^ out put) and analysis of the data by computer. Experiments were conducted using UV, visible, and IR stimuli. Results of the experiments are presented and discussed.
Response to UV and Visible Radiation
A response was obtained for all narrow bands of UV and visible radia tion except the band with peak wavelength at 0.798 microns. If this band is placed in the IR region, as some authorities would suggest (144), then it can be stated that response occurred for all UV and visible wavelengths used. The bandwidth of this narrow band of radiation was not determined, but the half width of the interference filter, used to reduce the stray radiation reaching the insects, was 11 mu. It may be of interest to the reader that the author observed a red glow by looking directly into the exit slits of the monochromator.
The longest wavelengths causing a response were those contained in the narrow band with a peak wavelength at 0.752 microns. Again, the bandwidth was not determined, but the interference filter used to reduce stray light had a half width of 12 mu. Thus, from the results of this study, the cut off wavelength for corn borer response to visible radiation appeared to be somewhere between about 0.745 and about 0.790 microns.
Before further discussion, it will be helpful to look at the computer plots showing the average COg output in cc of COg per hour per insect, each 93
plot being derived from three tests with a single treatment. Figures 17A
through 17N show the night responses for the UV and visible tests. Figure
17P is from tests with no stimulus. Note that the ordinates do not have
the same scale for the different plots.
Two traces are included in each figure. In some figures, it is diffi
cult CO follow each trace, and with others it is easy, for example Figures
176 and 17E respectively. From the latter, it may be seen that one of the
traces is made up of a waveform that repeats itself 20 times. This trace
is the mean response function, Y, defined in the Procedure section, and is
shown on each of the computer plots. The other trace, i.e., the nonrepeat
ing one, is the average CO^ output of 12 insects involved in three tests with a. single treatment and presented as cc/hour/insect.
The radiation treatment is identified on each figure in the upper, right-hand corner as well as in the figure caption. Times during which the stimulus was being delivered to the insects are indicated in Figures 17E and 17N, as typical examples. The narrow bands between the vertical lines represent the stimulus periods. At time zero, a stimulus-off event has
just occurred. This is true for all the computer plots shown.
Some of the variations in the patterns of CO^ output, from one radia
tion treatment to another, will be illustrated by reference to the plots.
Figure 17A shows a downward trend in the CO^ output; this is best observed
by noting the minimum points of the response curve. An upward trend is suggested In Figure 17G, and a still different trend pattern is seen in
Figure 17F, showing a broad peak. From the plots, it may be seen that amplitudes of response peaks may vary greatly from one stimulus period to the next; Figure 17D is a good example. The extent of variation in noctur nal activity, with time, is seen in Figure 17P, which shows the plot from
tests with no radiation stimulus. These factors were taken into account in
the statistical analysis.
Regression techniques were used to determine responses to the various
radiation treatments. The F statistic and Durbin-Watson d statistic (dis
cussed in the Procedure section) are given in Table 3 for each treatment.
Dates on which the tests were performed are shown, since this might have
been an important factor in the responsiveness of the insects. Magnitudes
of the F values are shown in the bargraph of Figure 18.
Responses were significant at the 1% level except for the 0.578 micron
treatment which was significant at the 57» level. Comparisons of the plots
and F values suggest the type of response pattern resulting in the larger F
values. For example, the largest F values resulted from the 0.365 (Figure
17C) and 0.405 (Figure 17D) micron treatments. These plots show smooth
response peaks of high amplitude. Also, the mean response function (repeat
ing waveform) is smooth and shows a sharp peak. The other extreme, for the
smallest significant F value, is shown in the plot for the 0.578 micron
treatment (Figure 171). Response peaks are irregular, and the mean
response function is not smooth and does not show a sharp, well defined
peak. If response peaks are smooth and show well defined peaks, the F
value is fairly large even if the amplitudes of the response peaks are not
large (Figure 17K).
It was hoped that the F statistic would not only serve as a test for significance of response but would also allow a comparison of response levels to the different radiation treatments. If this were the case, the bargraph of Figure 18 would provide a convenient indication of the relative 95
Table 3. Statistical data of nighttime (10:06 PM to 8:06 AM) UV and visi ble tests
Dates of Wavelength Durbin- F experiments (microns) Watson, d statistic
3/6 - 3/8 0.313 1.9470 7.154** 3/9, 3/10, 3/13 0.334 1.9187 7.605** 3/3 - 3/5 0.365 1.9155 13.535** 3/20 - 3/22 0.405 1.8479 16.394** 4/22, 4/23, 4/25 0.436 1.9533 7.739** 5/7 - 5/9 0.475 1.8841 5.514** 5/10 - 5/12 0.514 1.9251 8.155** 5/4 - 5/6 0.546 1.9513 7.237** 5/1 - 5/3 0.578 1.9266 1.632* 5/4 - 5/6 0.605 1.9533 3.204** 5/16 - 5/18 0.660 1.9071 13.340** 5/19 - 5/21 0.700 1.9532 12.150** 5/28 - 5/30 0.752 1.8838 5.424** 5/31 - 6/2 0.798 1.9256 0.777 3/15, 3/16, 3/18 No stimulus 1.9150 1.177
Significant at the 5/Ô level.
** Significant at the 1% level. responses to UV and visible radiation. There is a weakness in using this statistic as a means of comparison, however. For example, the F values for the 0.365 (Figure 17C) and 0.660 (Figure 17K) micron treatments are nearly equal, 13.5 and 13.3 respectively, even though the response peaks for the
0.365 micron treatment have a much larger amplitude. The height of the mean response function is 0.500 cc/hour/insect, whereas, it is 0.180 for the 0.660 micron treatment. 95
To obtain a more realistic comparison of responses, a response index,
(RI), was utilized, based on the mean response function. This index is
defined in the Procedure section. A bargraph of the response indexes is shown in Figure 19. Weak responses to the 0.578 and 0.605 micron treat ments and stronger responses in the far-red portion of the visible spectrum are still suggested, as was true with the F statistic but not to as large a degree. The RI values offer a logical comparison in the sense that they are based on response peak amplitudes which are proportional to insect activity.
Time relations between stimulus presentation and insect response can be determined from the computer plots, especially the mean response func tion trace. It is only necessary to look at the first complete waveform of the mean response function trace, because each waveform is identical and bears the same time relationship to the stimulus. One five-minute stimulus period terminates at time zero on the plots.
From Figure 17E, it is seen that, on the average, response did not occur at the time the stimulus was presented; the average response actually began several minutes before this event. A plausible explanation is as follows: when the stimulus was removed, the insects began the dark-adapta- tion process which took approximately 15 minutes, and the insects became active because of their nocturnal nature. With the recurrance of the stim ulus, the insects were at first excited by the stimulus, but after a short period of light-adaptation, their activity was inhibited. Thus, a cyclic pattern of activity resulted but with a 30-minute cycle which was hot in phase with the stimulus. The other plots would also allow this interpreta tion. It is interesting that the peak of the mean response function occurred
near the end of the stimulus period for all treatments resulting in
responses. Two possible causes are that the insects ceased activity in
response to darkness or inhibition of activity began after approximately
five minutes of the stimulus,
A number of responses, which apparently occurred as a direct result of
experiencing the introduction of the stimulus, were observed on the origi
nal recorder traces. The average time from the introduction of the stimu
lus to the initiation of insect activity was approximately one minute.
Times varied from a few seconds to about three minutes. For some of the
radiation wavebands causing the weaker responses, the individual responses
tended to be in closer phase with the stimulus than was true with the wave
bands causing stronger responses. This is evidenced by the plots 17K, 17L,
and 17M, where the mean response function begins it rise nearer the time of
the introduction of the stimulus.
Records of insect CO^ output obtained during the daytime portion of
each test revealed little if any response to the radiation stimuli during
the period from 12:06 PM to 10:06 PM. For this reason, only five selected
daytime records were computer processed. Plots of the records are shown in
Figures 20A through 20E. Two of the five treatments resulted in a signifi cant response, those with peak wavelengths at 0.365 and 0.700 microns. The
F values were lower than for the corresponding night records; these are
shown in Table 4 and in Figure 18. A downward trend of CO^ output is evi
dent in each of the daytime plots. The reason for this trend is not known,
but part of it is probably an adaptation period for the disturbed Insects. Figure 17. Computer plots of the rates of CO2 output of corn borers subjected to periodic UV and visible radiation. Each plot is the average of three 10-hour, nighttime records. Also shown is the mean response function waveform. Radiation peak wavelength is shown on each plot. A wavelength of .000 u indicates no stimulus. (Applies t:o Figures 17A-17P) NIGHT RESPONSE-5 MIN. .31-Ul RAD. EACH 30 MIH.
vO vO
O 00 "1 1 1 r— T 1 0.00 9.00 18.00 27.00 36.00 >15.00 SU.00 TIME IN MINUTES (xlO* I
Figure 17A 0.313 Microns NIGHT RESPONSE-5 MIN- .33401 RflD. EACH 30 MIN-
0.00 9.00 ,, 18.00 27.00 36.00 15.00 51.00 TIME IN MINUTES (xlO* )
Figure 17B 0,334 Microns NIGHT RESPONSE-5 MIN- .365Ji RAD. EACH 30 MIN.
IB.00 27.00 TIME IN MINUTES
Figure 17C 0.365 Microns NIGHT RESPONSE-5 MIN. .1405U RRD. EACH 30 MIN.
CJ lu in o (M V cc X
OJ -* o o
o 0.00 9.00 _ 18.00 27.00 36.00 TIME IN MINUTES
Figure 17D 0.405 Microns NIGHT HE5P0NSE-5 MIN- .»43Bll FlflO. ERCH 30 MIN
V
,, 18.00 27.00 36.00 45.00 sy.oo TIME IN MINUTES cxio» i
Figure 17E 0.436 Microns NIGHT HE5P0NSE-5 MIN. .»475W MAD. LnCH 3D MIN.
18.00 27.00 45.00 TIME IN MINUTES Cxio* )
Figure 17F 0.475 Microns NIUHT REISPCJNSE-S MIN. .51«4ji RHO. EACH 30 Mir4.
o CD
O a»
O LU
-cvi oc z:
«k. C\J«- o u
o 03 T 0.00 54.00 TIME°IN MFNUTES
Figure 17G 0.514 Microns NIGHT MEbPONSE-5 MIN- .546)1 HAD. EACH 30 MIW.
a to
o 3»
u LU
-(M-» .
CC 3: \ L_)
* . fXir-' O O
O 00
0 00 18.00 27.00 45 00 'W. OU TIME IN MINUTES (xXQi I
Figure 17H 0.546 Microns NIGHT RESPONSE-5 MIN. -57au mo. EACH 30 M IN
\
T r 0.00 16.00 27.00 36.00 45.00 51-. 00 TIME IN MINUTES 1x10% J
Figure 171 0.578 Microns NIGHT RESPONSE 5 MIN. .605U RAD.EACH 30 MIN. o CD
O
L_) LU tn C) o oo
CO
•JO
0 OU 9.00 16.OU 27.00 36.00 TIME IN MINUTES
Figure 17J 0.605 Microns NIGHT PlESPCJNSE-5 MIN. .6601.1 RAD.EACH 30 MIM.
o (O
O a»
(_) UJ
-fu
CC
A .
O u
o OD -1 1 1 1 1 ~I 0.00 9.00 16.00 27.00 36.00 us.00 su uo TIME IN MINUTES (x,l0^ )
Figure 17K 0.660 Microns NIGHT RESPONSE-S MIN. .70aU RAD.EACH 30 MlN-
M o
-l —1 1 1 ~i 0.00 9.00 IB.00 27.00 36.00 54.00 TIME IN MINUTES
Figure 17L 0.700 Microns NIGHT RE3P0NSE-5 MIN- .752U ROD. EACH 30 MiN.
o oo
o (O o LU
-a»
or.
k*. c\j— o o
o O 1 0.00 18.00 27.00 36.00 US.00 SU.00 TIME IN MINUTES (xAO* 1
Figure 17M 0.752 Microns NIGMT RESPONSE-5 MIN. .79BM RRD.ERCH 30 MI M.
o o (M o LU (/)_ ro OC X ug « . OJ-*' o CJ o O) 0.00 9.00 ,18.00 27.00 36.00 US.00 54.00 TIME IN MINUTES UIO* 1 Figure 17N 0.798 Microns C02,CC/HR/rNSECT 0 .00 1.20 1.40 1.60 1.80 -Uu/JIF .00 1 1 1 1 1 9.00 Figure 17P < TIME 18.00 1 IN MINUTES 27.00 < No stimulus 36.00 ï uio» ) 45.00 -OODU NIGHT RESPONSE-5MIN 1 RAD. 54.00 EACH 30 1 Ml4 - h-* o> h-* Figure 18. Significance of responses of corn borer to UV and visible radiation from 0.313 to 0.798 microns S 18 s i s- « 16 a> o Z 14 o N 12 \ \ c \ o 10 în 9 C) >o 8 Sd c> o C) N \ s s $ \ \ R 6 S s \ O \ \ \ \ \ \ 4 Significance \ \ \ oo Levels s \ \ m CO S 2 \ \ s ïs M \ S 0 i. JSL .4 .5 .8 Wavelength (Microns) Figure 19. Average responses of corn borer to UV and visible radiation from 0.313 to 0.798 microns w zzzzzzzzzzz: / / y1 0 ,313 Microns //y / 3 0.334 zzzzzzzzzz: / // ///AZZZZ y// / 0.405 / / /////i ///////////I 0.475 o < ' o ZZZZZZZZZ3 0.514 5 / ///J0.578 q'. o ZZZZZl 0.605 3ut ] 0.660 ZZZZZZZZZl 0.700 0.752 CO pTTI 0.798 Figure 20. Computer plots of the rates of CO2 output of corn borers subjected to periodic UV and visible radiation. Each plot is the average of three 10-hour daytime records. Also shown is the mean response function waveform. Radiation peak wavelength is shown on each plot. (Applies to Figures 20A-20E) DAY RESPONSE-5 MIN. .365a RAD. EACH 30 MI M. 8 o w •4 # oc X % OJ-»' o o 1 1 0.00 9.00 18.00 27.00 36.00 US.00 SU.00 TIME IN MINUTES txlO* ) Figure 20A 0.365 Microns DAY R&5PQNSE-5 MIN- .570)1 RAD.EACH 30 MIN. o O (M O LJJ ina •—«o, cc X AAA^ \ rum O (_) o OD oô 0.00 9.00 18.00 27.00 36.00 US.00 SU.00 TIME IN MINUTES (xlQi ) Figure 20B 0.578 Microns DAY RESP8N5E-5 MIN- .60511 RAO. EACH 30 MIN. o -,00 Lsi- O) "T 1 1 r T ~T 0.00 9.00 18.00 27.00 36.00 «15.00 SU.00 TIME IN MINUTES ixio^ i Figure 20C 0.605 Microns DAY RESPQN5E-5 MIN- .700U RAD. EACH 30 MI M. to »—<(\j_ 1 — 1 0.00 18,00 27.00 36.00 US.00 54.00 TIME IN MINUTES (xlQl J Figure 20D 0.700 Microns I DAY RKSP0N5E-5 MIN. .79BA RflD- EACH 30 MIN \H\ 1 r 0.00 9.00 18.00 27.00 36.00 US.00 TIME IN MINUTES (xio* ] 5U.00 Figure 20E 0.798 Microns Table 4. Statistical data of daytime (12:06 PM-10:06 PM) UV and visible experiments Wavelength Durbin-Watson F (microns) d statistic statistic ** 0.365 1.9869 3.127 0.578 1.9157 0.401 0.605 1.8182 1.045 0.700 1.9458 2.773** 0.796 1.9179 0.428 Significant at 1% level. Response to IR Radiation No responses were obtained for the four wide bands of IR radiation. Plots of the rate of CO^ output are shown in Figures 21A through 21F. Although an analysis of the data revealed no significant F values, the plot of the 8.5-15 micron tests (Figure 2ID) suggests a possible response. Addi tional tests were conducted using this waveband, but no response was indi cated by these records. The plot shewn in Figure 2IE is an example. Values of the F statistic are shown in Table 5 and Figure 22. As an additional criteria of the influence of the radiation on the corn borers' activity, females were examined after each test to determine if mating had occurred. Out of a total of 126 females used in 63 tests, 21 were mated. Low mating efficiency was due, in part at least, to the young age of the insects. Generally, mating efficiency is low for the first Figure 21. Computer plots of the rates of CO2 output of corn borers subjected to periodic IR radia tion. Each plot is the average of three 10-hour nighttime records. Also shown is the mean response function waveform. Radiation waveband in shown on each plot. A waveband of 0.000 u indicates no stimulus was used. (Applies to Figures 21A-21F) NIGHT RESPONSE-5 MIN. 1-311 RRD. EACH 30 MIN. o o o (\J ÛC an CO 0.00 9.00 18.00 27.00 TIME IN MINUTES 96.00 Figure 21A 1-3 Microns NIGHT RE5P0NSE-5 MIN 3-6U RRD. EACH 30 MIN S CJ UJ -a» OC & A . f\J—' O (_) S "1— 1 1 1 1 0.00 9.00 IB.00 27.00 36.00 45.00 sy.oo TIME IN MINUTES [xlQi ) Figure 2lB 3-6 Microns NIGHT.ME5P0NSE-5 MIN. S-llkWFJRD. EACH 30 MIN. 00 C_) UJ tn ho o CO I—I oc 3: o 0.00 9.00 LB.00 27.00 36.00 TIME IN MINUTES ixio» j Figure 21C 5.3-10 Microns NIGHT RESPONSE-5 MIN. 8-Ï5U RAD EACH 3D M IN. , IB.00 27.00 TIME IN MINUTES Figure 21D 8.5-15 Microns NIGHT RE:SP0NSE-5 MIN 9-I5W RAD. EACH 30 M(N. o 09 O o J-j 1 -l 1 1 1 1— 0.00 9.00 LB.00 27.00 36.00 45.00 54.00 TIME IN MINUTES uio^ J Figure 21E 8.5-15 Microns NIGHT RE5P0NSE-5 MIN .OOOU RAD EACH 30 MIN , IB.00 27.00 TIME IN MINUTES Figure 2IF No Stimulus Figure 22. Significance of responses of corn borer to bands of III radiation from L to 15 microns .6 1.52 5% .4 Significance Levels .2 25% .0 1-3Microns i/> 0.8 u_ «0.6 5.3 - 10 0.2 0.0 0 4 6 8 1 0 1 2 1 4 Wavelength (microns) 134 Table 5. Statistical data of nighttime (10:06 PM-8:06 AM) IR experiments Date of Wavelength Durbin-Watson F experiments (microns) d statistic statistic 4/12 - 4/14 1-3 1.8748 0.739 3/24 - 3/26 2.5-6 1.8737 0.609 3/27 - 3/29 5.3-10 1.9123 0.431 4/2, 4/3, 4/5 8.5-15 1.8585 1.108 4/15, 4/16, 4/18 8.5-15 1.9190 0.823 4/7, 4/8, 4/10 Mo 1.8918 0 = 591 night after the night of emergence. No correlation between mating and radiation stimulus was apparent for the UV, visible, or IR tests. Critique of the Techniques Experimental Monitoring of the insects' CO^ output served as a simple and conve nient means of detecting response to the radiation stimuli. There is no assurance, of course, that all types of response to the stimuli resulted in a change in CO^ output rate. However, it is certain that flight activity and other locomotion responses were detected. The technique was especially useful with UV and IR experiments since visual observation was not possible. Also, this method did not require directional movement of the insects as is required for the choice-chamber technique. Another desirable feature was the continuous or essentially continuous record of activity obtained. The actual respiration pattern was not 135 exactly reproduced on the recorder trace, due to niixing of gases in the components of the system and, to a lesser extent, the response times of electronic components, but the traces were adequate for the purposes of the study. Methods of obtaining COg-free air with a specified temperature and rh, of controlling the flow-rate of the air, and of controlling the temper ature of the insects' environment were simple and effective. The columns for drying and removing odors and CO^ from the air appeared to give satis factory results for three months without replenishment. Air flow-rate required adjustment approximately every five days. Some poââible disadvantages of the technique will be mentioned. In stimulus-response studies with animals, a phenomena called temporal condi tioning may occur; a given stimulus response begins to appear even in the absence of the actual presentation of the stimulus, if the latter is delivered in a periodic fashion. Limited tests were conducted to examine this possibility. A UV stimulus was presented, periodically, until a strong response pattern developed. When the stimulus was removed, there was no evidence of a continuing periodic response, even for a single cycle. For the present study, the existance of temporal conditioning would not have precluded conclusions concerning the presence of responses to the radiation stimuli, but phase relationships between stimulus and response times would be affected. An important aspect of the study was the periodic manner in which the stimulus was presented. Up until the time of a test, the insects were maintained in a photoperiod similar to that of their natural environment. It is possible that the severe change in the photo-regime Inhibited response. 136 Inhibition of response sight have been caused by the small insect chamber. Sustained flight times did not usually exceed eight minutes, regardless of the stimulus. However, there was considerable flight activ ity during the nonstimulus tests, indicating that activity was not strongly inhibited by the chamber. Data collection and processing The DC output of the CO^ analyzer, corresponding to the varying levels of COg in the test gas, afforded convenient interfacing with the data acquisition system. Recording of information on punch-paper tape and sub sequent processing resulted in statistical evaluation of the data with few hand operations and calculations. Accumulation of data for all experiments on a single magnetic tape simplifies storage and allows additional analysis in the future, if desired. By visual observation of the recorder traces of CO^ output, all responses were predicted, except for the response to the 0.578 micron treat ment which was questionable. A response was suspected for one of the IR treatments, but the statistical analysis showed nonsignificance at the 5% level. The analyses added confidence to what appeared to be responses and gave some quantitative comparison. Other interesting information was revealed by the regression analyses. The third order autoregressive model indicated that the calculated CO^ out put rate, at a particular time, was sometimes influenced by the CO^ output rates occurring as much as three minutes away. This might have been caused by the system response time, associated with the mixing of gases in the system. Another reason may have been the tendency of the insects to be 137 active or inactive for several minutes at a time, not being purely random in the times of their flight activity. Time trend and time trend-mean response interaction terms accounted for variations in the response records. Terms up to cubic were necessary to describe the time trend contained in some of the records. These three terms may be visualized as defining a curve passing roughly through the minimum points of the response curve. The interaction terms show that the amplitudes of the response peaks may have a cubic trend, with time. Discussion A technique for measuring insect response to periodic radiation stim uli was developed, based on continuous monitoring of respiration rate, and relative responses to various wavelengths were at least suggested. Rela tive responses obtained for UV and visible radiation agreed with the find ings of other researchers with one possible exception. It has been gener ally reported that most insects display no response or a weak response to visible light at wavelengths very near the IR region. The present study, however, revealed a significant and relatively strong response, up to a narrow band with peak wavelength at 0.752 microns. No statistical analyses were made to establish differences in responses for the different treatments other than by comparison of the statistical F values. Quantitative comparisons resulted from measurements derived from the collected data, without statistical treatment. The records show that the strongest response occurred in the near UV. As has been stated, no response was obtained for the narrow band with peak wavelength at 0.798 microns or for wavelengths from 1 to 15 microns. 138 The radiation treatments were not randomly applied with respect to time. Usually, tests with a specific wavelength were conducted on succes sive days, and, generally, experiments were carried out in order of wave length magnitude, but there were several exceptions to this. If time (of month or year, for example) was an important factor, the results contained this bias. Field studies have indicated that the corn borer moths become active approximately two hours after sunset. Laboratory studies show activity beginning approximately two hours after the photoperiod termination. In this study, development of the insect from the egg stage tc the adult stage took place under a photoperiod that terminated at 12 midnight. If the time of nocturnal activity was governed by a circadian rhythm established during insect development, initiation of activity might be expected to occur about 2 AM. Activity usually began between midnight and 2 AM. Examination of the CO2 output records suggested a gradual change in the time at which the nocturnal activity began. It appeared that the period of activity did not vary much from one night to the next but would vary up to two hours over a period of several weeks. Statistical analyses verified what appeared obvious from the CO^ out put records, that best results were obtained during the night. Day responses were weak and irregular for all treatments. However, it is interesting that the insects often showed strong response to UV and visible stimuli for approximately two hours after being introduced into the test at 8:45 AM. Data collection was not begun until 12:06 PM; hence, this morning part of the record was not Included in the analyses. This response- was usually of the same order of magnitude as the later night response for the same test. Absence of response to IR radiation from 1 to 15 microns does not necessarily indicate that the insect did not sense the stimulus. Negative results are not conclusive in the sense of disproving detection capabili ties. It can only be stated that under the conditions of the experiments, the IR stimuli did not influence the respiration rate of the insects. 140 SUMMARY AND CONCLUSION Investigations were carried out to develop a technique for measuring insect response to periodic radiation stimuli and to determine responses of the adult European corn borer, Ostrinia nubilalis (Hubner), to ultraviolet (UV), visible, and infrared (IR) radiation with wavelengths from 0.313 to 15 microns. The technique included continuous monitoring of the insects' respiration rate (CO^ output) as a response criteria, recording of the COg output on punch-paper tape, and computer analysis of the data. A continuous flow of C02-free air, of specified temperature and Yh, was delivered to an insect chamber containing two male and two female insects. Through respiration, the insects added CO^ to the air, the amount added being proportional to their physical activity. This air was passed through an IR CO^ analyzer, which gave a continuous indication of the res piration rate of the insects. A data acquisition system was used to record, on punch-paper tape, the millivolt signal from the CO^ analyzer. Information on the paper tape was transferred to magnetic tape to facilitate computer processing of the data. Radiation stimuli were delivered to the insects for five minutes every 30 minutes over the 20 hours of each test. Treatments included three nar row bands of UV, 11 narrow bands of visible, and four wide bands of IR radiation. The UV and visible bands were furnished by a single-pass, prism monochromator, and the IR bands were obtained by use of an IR source and wide-band interference filters. Radiation intensity levels were 2 approximately 6 microwatts/cm for the UV and visible tests and 120 micro- 2 watts/cm for the IR tests. 141 Regression techniques were used to analyze night and day portions of the response records separately. Because of the circadian pattern of activity of these nocturnal insects, the night portion of the records con tained the majority of response information. Responses were obtained for all UV bands. The peak wavelengths were 0.313, 0.334, and 0.365 microns. Responses were obtained for ten of the 11 visible bands. For the ten bands causing responses, the peak wavelengths were 0.405, 0.436, 0.475, 0.514, 0.546, 0.578, 0.605, 0.660, 0.700, and 0.752. No response was obtained for the band with peak wavelength at 0.798 microns. No responses were obtained for the 4 wide bands of IR radiation. These bands were as follows: 1-3, 2.5-6, 5.3-10, and 8.5-15 microns. Comparison of responses to the different UV and visible wavebands was made by determining the average response peak height and adjusting this average height for the general level of respiration for each treatment. This comparison showed maximum response in the near UV, at 0.365 microns. Responses were strong to moderate for the eight bands with peak wavelengths from 0.313 to 0.546 microns, weak for bands with peak wavelengths at 0.578 and 0.605 microns, and moderate for bands with peak wavelengths at 0.660, 0.700, and 0.752 microns. The study led to the following conclusions: (1) Measurement of the adult European corn borers' activity response to periodic radiation stimuli may be accomplished by continuous monitoring of the insects' CO^ production. (2) The technique developed, which utilizes an IR CO^ analyzer to measure the CO^ output of the insects, a data acquisition system with punch-paper tape output to record the CO^ output data, and 142 computer analysis of the data, can be utilized for measuring and statistically establishing the insect's responses to periodic radiation stimuli. 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January 20. 1969. 143. Shorey, H. H. and Gaston, L. K. Sex pheromones of noctuid moths - V. Circadian rhythm of pheromone-responsiveness in males of Autographa californica, Heliothis virescens, Spodoptera exigua, and Trichoplusia ni (Lepidoptera: Noctuidae). Entomological Society of America, Annals 58: 597-600. 1965. 144. Simon, I. Infrared radiation. Princeton, N.H., D. Van Nostrand Co., Inc. 1966. 145. Sparks. A. N. Biotypes of European corn borer populations in the mid west. Unpublished Ph.D. thesis. Ames, Iowa, Library, Iowa State Uni versity of Science and Technology. 1965. 146. Sparks, A. N. Preliminary studies of factors influencing mating habits of the European corn borer. North Central Branch, Entomological Society of America, Proceedings 18: 96. 1963. 147. Sparks, A. N. The use of infrared photography to study mating habits of the European corn borer. North Central Branch, Entomological Soci ety of America, Proceedings 18; 96. 1963. 148. Sparks, A. N., Chiang, H. 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The effects of variations in atmospheric pressure on insects. Canadian Journal of Research 24: 51-70. 1946. 174. Williams, C. B. An analysis of four years captures of insects in a light trap. Pt II The effects of weather conditions on insect activity. Royal Entomological Society of London, Transactions 9: 227-306. 1940. 175. Winfree, A. T. Biological rhythms and the behavior of populations of coupled oscillators. Journal of Theoretical Biology 16: 15-42. 1967. 176. Winget, C. M., Card, D. H. and Pope, J. M. Circadian oscillations of three parameters at defined light intensities and color. Journal of Applied Physiology 24: 401-406. 1968. 177. Wolfe, W. L., editor. Handbook of military infrared technology. Wash ington, D.C., Office of Naval Research, Department of the Navy. 1965. 178. Wong, C. L. and B le vin, W. R. Infrared reflectances of plant leaves. Australian Journal of Biological Science 20: 501-508. 1967. Zimsernian, W. F., Pittendrigh, C. S. and Pavlidis, T. Temperature com pensation of the circadian oscillation in Drosophila pseudoobscura and its entrainment by temperature cycles. Journal of Insect Physiology 14: 669-684. 1968. 158 ACKNOWLEDGMENTS Appreciation is expressed to: Dr. L. F. Charity for serving as major professor and for assistance in all phases of this study. The Graduate Committee, composed of Drs. L. F. Charity, T. A. Brindley, J. W. Nilsson, G. W. Peglar, L. B. Altman, and C. W. Bockhop, for guidance and encouragement during the entire graduate program. The Investor-Owned Electric Utility Companies of Iowa who provided financial support for this investigation. The U. S. Department of Agriculture for their organizational policy which allowed me to complete the Ph.D. program under their employment. The many persons, including personnel of Iowa State University, Ames Laboratory of the Atomic Energy Commission, and the U. S. Department of Agriculture, for their cheerful and expert advice on problems of the study related to their fields and for making valuable equipment available for our use. The following should be mentioned: Dr. R. N. Kniseley, Dr. Wayne Fuller, Dr. Leslie Lewis, Mr. Leo Soderholm, Mr. Robert Lynch, Mr. Wendell Primus, Mr. Clifford Olson, and Miss Evelyn Conrad. 159 APPENDIX A. IR RADIATION THEORY AND SAMPLE PROBLEM 160 Radiant energy can be expressed quantitatively by considering the heat added to a perfect absorber (blackbody) as the radiation is fully absorbed. Also, the quantity of photons in radiant energy can be determined if the exact radiation spectrum of the emitter is known since photon or quantum energy, at any given frequency, is known. Relationships between wavelength, frequency, and energy are described by two simple equations, namely A = c/v and E = h v where c = velocity of light in a vacuum h = Plank's constant \= wavelength E = energy of the quantum or photon V= frequency These relationships, along with the appropriate boundaries of designated bands, are illustrated in Figure 2, located in the Procedure section. Some of these ranges overlap. Additional information related to detection of the radiation, mode of absorption, and effect of absorption is presented in Table 6. Various colors are accepted as a part of our environment, without much question; that the different colors exist and help with identification is obvious. Not so obvious are the patterns of UV and IR radiation. For a total picture of these radiation patterns, many phenomena must be taken into account including greybody emission, absorption, scattering, reflec tion, and others (98, 177). Because of the possible involvement of IR radiation In insect communi cation, a short discussion of theory will be presented. IR follows the Table 6. Summary of information pertaining to the electromagnetic spectrum Radiation band Wavelength Frequency (Hz) 16 Ionizing <.1 microns 3 X 10 Ultraviolet .1-.4 microns ! Ï 15 .4-8 microns 8 X 10 Visible 14 3.8 X 10 14 Near infrared .8-25 microns 3.8 X 10 13 1.2 X 10 13 Far infrared 25-125 microns 1.2 X 10 12 2.4 X 10 12 Millimetric 125-10,000 microns 2.4 X 10 10 3 X 10 10 Centimetric (SHF) 1-10 cm. 3 X 10^ 3 X 10' Decimetrie (UHF) 10-100 cm. 3 X 10 8 3 X 10 8 Metric (VHF) 100-1,000 cm. 3 X 10 3 X lO' Low to high 1,000 cm. 3 X 10' 162 Responsive element Absorbed by Effect of absorption Ionization chamber Nucleus Ionization Film Electron cloud Electronic excitation or ejection of K- shell electrons Film Electron cloud Excitation or ejection Photocell of L, M shell, or valence electrons Film Electron cloud Excitation of valence Photocell electrons Eye Film Vibrating permanent Increase kinetic Photocell dipoles in molecules energy of dipoles Skin sensor Film Rotating and vibrating Increase kinetic Skin sensor permanent dipoles in energy of dipoles Bolometer molecules Skin sensor Rotating permanent Increase kinetic Tuned capacitor- dipoles in molecules energy of dipoles inductor circuit Tuned capacitor- Rotating permanent Increase kinetic inductor circuit dipoles in molecules energy of dipoles Translation Tuned capacitor- Translation Unknown inductor circuit Body sensor Tuned capacitor- Translation Unknown inductor circuit Tuned capacitor- Translation Unknown inductor circuit Induction heating wave, and other radiation. Having the same nature as all radiation, it also comes under the radiation law first proposed by Planck, involving the quantum concept. Its location in the electromagnetic spectrum is shown in Figure 2. IR energy with wavelengths near the visible red is known for its abil ity to heat objects in its path. The energy per photon decreases in the IR compared with the visible, the decrease continuing by a set law as the wavelength increases, but due to extensive absorption of short wavelength Any object or substance, solid, liquid, or gas, having a temperature, emits IR radiation. As an approach to understanding this emission, a black- body is postulated that has the characteristic of absorbing all radiation falling upon it. It is also the most effective radiator, and the spectrum of emitted radiation can be described mathematically. In practice, the most perfect blackbody radiator is realized by forming a cavity in a suit able material and allowing the radiation to escape from the cavity through a small aperture. This type of structure allows a radiation balance to be achieved between the cavity and the walls. Considering the several modes of oscillations taking place with the molecules in the cavity wall and applying proper statistics leads to the expression for the rate of flow of radiant energy, W, per unit area of aperture in the wavelength increment dA at wavelength \ . It is ZTThc d where 164 h = Planck's constant c = velocity of light in a vacuum k = Boltzmann constant T = temperature in degrees Kelvin The equation for wavelength of maximum energy can be found by differ entiating the above with respect to X» It is ^ max = K/T where K = 2898 micron degrees if X is measured in microns. Integrating with respect to A yields, upon some combining, W = I V = CTT^ A=o where W = total radiant emittance -12 -2 -4 -1 O' = Stefan-Boltzmann constant = 5.673 x 10 watts cm deg sec The perfect radiator would have an emissivity, £ , of 1; a real body has a value less than 1, i.e., they are not perfect absorbers. Total radi ant emittance becomes W =€ All substances are subjected to external radiation which is either transmitted, absorbed, or reflected. Absorbed energy, in turn, then influ ences the state of the substance and its own emission spectrum; there is a constant exchange of energy going on. Insects, as all other observers, are presented with a radiation pattern resulting from these various phenomena. Emitted radiation has been looked at thus far as coming from a body or substance based on its temperature and absorbtive and reflective properties. There is also line emission from specific molecular events; definite wave 165 lengths are given off, as discrete energy changes occur on the molecular level. These changes may result when the molecules are subjected to other radiation, heat, or other forces. In general, the absorption and emission of UV and visible radiation are associated with energy changes in the elec tron structure of molecules while IR absorption and emissions involve energy changes in the vibration and rotation modes of molecular action. The relationship between wavelength and energy change is expressed by A = hc/E where E = energy of a quantum. Thus, wavelength is fixed for a given energy shift. Line émission is mentioned because it may be important to the insect world. Familiar line spectra are those from gas discharge lamps and flames. Some sources in nature are already known; others may be dis covered. The source of emitted or reflected radiation would probably be the target when considering communication among insects. Consideration of detection of this radiation brings a new set of questions. Involved is some type of detector on the receiving insect. Absolute-aiid practical limits of detection exist, regardless of the type detector. The actual limit depends on many factors such as the operating principle of the detec tor, its size, the radiation collecting area, background radiation, field of view, and discrimination features (98). Types of applicable detectors depend on the wavelengths and energy levels to be detected (98, 142). Capabilities are expanding at a rapid rate through improved sensing elements and techniques: In this technical field, an expression that occurs frequently is Noise-Equivalent Power (N.E.P.). With a thermal detector, this is the radiation noise generated within the detector itself, by virtue of its own temperature, eaisaivity, and bandwidth. The value of N.E.P. can be calculated on theoretical grounds, for each type detector (98). Reception of a signal of size equal to N.E.P. results in a signal-to-noise ratio of one. For detector compari son purposes, an expression, detectivity (D*), is often used. It is defined by D* = (AAf>^/N.E.P. where A = area of sensitive element of detector Logic will suggest some of the approaches to obtaining good detection capabilities and also suggest the disadvantages of certain approaches. For example, if construction of the detector is such that a small, distant tar get could fill the field of view, the detection capability might be great. But to have to search for a target with a detector having such a small field of view is likely to prohibit its use. A mosaic of detector elements, each pointing in a slightly different direction, might be useful, although the processing of the numerous signals would be a major problem. Periodic interruption or some other encoding of the radiation, from the source, and corresponding design in the detector to take advantage of this encoding can lead to the ability for detection of signals much smaller than the back ground radiation. The method of cooling detectors to lower the N.E.P. is used but is not likely with insects. In combination with the actual sensing element of a detector, one might find waveguides, antennae, radiation collecting devices, and other structures. With antennae or waveguides, it would be necessary to have a mechanism of some type to convert the small energy of the waves to a nerve impulse. Use of waveguides and antennae with microwave and radio frequen cies assumes coherent radiation; the same would probably be true with insects, provided they employ waveguide or antennae-like structures to detect IR radiation. Another concept of detection is photon or quantum detection (98). The energy of incident photons displaces charge carriers which become free for conduction processes (photoconduction), or electrons are emitted from metal surfaces into a vacuum with energy change dependent on the photoelectric work fuTiction (photocmlsslori). Fuotoconductlori is uôcful for short wave lengths including those in the visible. Photoemission is used with longer wavelengths reaching into the near IR. Quantum detectors are not very use ful with the longer IR wavelengths because the photou energy is small. Whatever the mechanism, it has been reported that the eye of a certain insect is capable of detecting a few quantum of visible radiant energy. The suggestion was made that a detection threshold may not exist; the eye may be capable of detecting a dingle quantum (132). Study of the emission spectra and transmission properties of the earth's atmosphere is adding to our knowledge of radiation patterns at this level. For example, there is a different IR spectrum, at night, looking directly upward as compared to looking toward the horizon. Each spectrum depends on ambient temperature, cloud conditions, and other factors. View ing with an elevation angle of 90°, there is a low intensity of 9 to 12 micron radiation (92). An insect, several degrees above the ambient tem perature and flying overhead, might "shine" against this background, for a receiving insect on the ground. 168 Included in the atmospheric radiation pattern is spectra from CO^, G^, N^, and water vapor, which may be important in insect activity. Since gas concentrations are correlated with weather, terrain, and vegetation, this could serve to draw insects to areas desirable for their survival. For information on atmospheric radiation, emission, and transmission under various atmospheric conditions, one may refer to the Handbook of Military Infrared Technology (177). A simple example will illustrate some of the concepts and problems associated with emission from, and detection of, a small greybody located ac a point in the earth's atmosphere. Assume a target with a relatively flat 1 cm^ side, at a temperature 10° C. above ambient, and with an emis- sivity factor of 0.9. For an ambient temperature at 25° C., the total energy from the target is target' ^ = (0.9)(5.673 x 10'^^)(308)^ = 4.6 X 10 watts/cm 2 Assume a 1 mm detector of unspecified type but with the property of scanning and having an instantaneous field of view of 1 square-meter at 10 meters. Assume no energy loss between the target and detector, which are 10 meters apart, and that the target and detector element are both perpen dicular to a line between them. By Lambert's cosine law, the detector would be subjected to: J = Cos -e- = ^ ) Cos 0° = 1.465 X 10"^° watts Td^ IT (lOT)^ The clear night sky, viewed at a zero elevation angle, radiates approx imately like a blackbody at the ambient temperature. From the 1 square- meter, the energy would be 169 W = CTT^ = (5.673 x 10'^^)(298)^ = 4.47 x lO'^ watts/cm^ "background = C*'*? » iO-'XlO^)' = 447 »a«s That received by the detector is J = ) = 1.423 X 10"3 watts Thus, the target would influence the total energy very little. Even with periodic interruptions or coding, the detector would have to be extremely well designed to discriminate between the background and target combined and the background alone. To continue this example, assume a wavelength sensitive detector, receiving only wavelengths between 9 and 10 microns. "Die energy from the target, in this bandwidth, is 3.7402 X lO'lZ (1,4385/10'^)(308) .-1 " ° (10-3)5 ^target = Assume the target to be at an elevation angle of 30°. InformaLion is available from data taken at Cocoa Beach, Florida, (1,77) which gives the spectral radiance at 10 microns, at a 30 elevation angle, as 400 microwatts -2 -1 -1 cm sr micron . Then, from the background, "background = (4°° « = 4 watts Equal percentages of the emitted radiation from target and background would 2 reach the detector. If the field of view was reduced to 100 cm , the back- ground value would become 4 x 10 watts, just an order of magnitude greater than the target output in this bandwidth. Add modulation of the target output and corresponding discrimination capabilities in the detector and detection becomes easily realizable. 170 Consideration of systems in insects for encoding and decoding is not idle thought. The firefly uses such a system (57). Also, the firefly sig nal has a chemical basis, and a relatively narrow frequency band of radia tion is involved. Perhaps a similar situation exists in the IR. Use of IR patterns for various purposes immediately seems more plausible when one looks at the striking detail and wealth of information afforded by IR pho tography, especially when obtained with wavelength-specific equipment and film. 171 APPENDIX B. DEVELOPMENT OF THE RESPIRATION MONITORING TECHNIQUE AND ITS APPLICATION TO SEVERAL TYPES OF EXPERIMENTS 172 Procedural problems, encountered during the early phases of this study, have not been emphasized thus far. Considerable time was spent in arriving at the techniques employed in the formal experiments. Some of the prelimi nary investigations will be presented in the following paragraphs. At first, it was thought desirable to utilize a closed-air system which would contain the CO^ produced by the insects. In this way, the COg could build up over an extended period of time giving a sensitive indica tion of the insects' output. The initial system contained a pump, moisture source, drying column, filters, the insect chamber, and other components. sing of CO^ made measurement of the CO^ output of the insects impossible. Even a simplified system containing only a pump and insect chamber connected with glass or stainless steel tubing was not satisfactory because a suitable pump could not be found. If the closed-air system had been workable, there would have been the concern of an increasing CO. concentration in the insect?' environment, whereas in the open system this level remained 'fairly constant. It is the opinion of the author that a closed system would have little or no advan tage over the open system, for most studies. Attempts at construction of the closed system were based on considera tion of the COg output of a single corn borer moth and the capabilities of the COg analyzer. However, use of four insects in each experiment, a slow rate of air flow, and amplification of the millivolt signal from the gas analyzer rendered the open system satisfactory. It is evident that with any type of system the experimenter should begin with the most simple con struction possible and add components one at a time, evaluating the influ ence of each. Another consideration was the relation between activity of corn borers and their CO^ output. A review of the literature revealed that the metc- bolic rate of insects, in general, increases with activity, usually by sev eral hundred percent or more. It was easy to confirm this for the corn borer. By visually observing the insects, the COg output was noted for various types and degrees of activity. Under the conditions of the experiments, the insects displayed inhibi tion of activity if presented with continuous UV or visible radiation. Tests lasting several hours showed that for day-old moths, inhibition per sisted as long as the radiation was presented. Older moths were more likely to be active during radiation periods. Thus, the possibility of using inhibition of normal, nocturnal activity was considered as a criteria of response to the radiation. The final practice of pregepti^ng^ the radia- - .• • tion for 5 minutes every 30 minutes was an attempt to utilize both active and inhibitory phases of response. Trial tests indicated a strong influ ence by UV with peak wavelength at 0.365 microns. Combinations of intensi ties, at this wavelength, and time programs of presenting the radiation were investigated. The objective was to acquire a CO^ output trace resembling, as near as possible, a full-rectified sine wave. Data in this form would yield a maximum amount of information upon spectral or regres sion analysis. Tests were conducted to determine the effects of temperature on insect activity. Initial plans were to conduct all tests with the Insects' environment maintained at 80° F. However, since average nightly tempera 174 tures in the field are less than 80° F., a lower temperature of 70° F. was investigated. The CO^ output of the inactive insects was less. Also, the level of nocturnal activity was reduced, and response to the stimulus was less pronounced. Thus, the 80° F. temperature was used as first proposed. Tests were performed to determine if the insects' CO^ output was affected by the level of CO^ in their environment. Outputs were found to be the same for levels near zero ppm and 320 ppm of COg. Hence, it was assumed that introducing COg-free air to the test insects was a satisfac tory procedure. This assumption may need more verification. ^ w ***»# &.*««* ws.^ w ^ V A w jr wy w ration rate should be useful for many types of stimulus-response and other biological studies. Several minor experiments, conducted in the author's laboratory, will illustrate the potential of the technique. Because of a report (105) that the antennae of a certain species of insect appear to be involved in detection of UV radiation, several tests were conducted with corn borers having antennae intact and others with at lease 90% of the antennae removed. Six tests, each involving 2 males and 2 females, were conducted. The insects were irradiated with narrow-band radiation peaking at 0.365 microns, for 12 minutes of each hour. Radiation intensity was not quantitatively determined but was maintained at a con stant level for all tests. Response was evaluated on the basis of the num ber of COg peaks corresponding to the stimulus periods and the heights of these peaks as determined from the recorder trace. With antennae removed, definite response peaks occurred for 54 of 63 stimulus periods compared to 56 of 64 with the antennae intact. A statis 175 tical analysis was carried out to compare the response peak heights resulting from the two treatments. No difference was found. An experiment was conducted using a combination of radiation stimuli and a falling temperature during night hours. These conditions were offered in an attempt to more closely approximate field conditions at night. For these tests, the four wide bands of IR were individually combined with a weak, continuous background illumination, furnished by a green-coated incandescent lamp, which was barely visible to the dark-adapted human eye. To facilitate this combination, a stainless steel cylindrical chamber was designed to allow mounting of optical windows on each end. The temperature was dropped from 80 to 73° F. in about 3 hours, starting at 12 midnight. The water column in the air flow, line was allowed to remain at the room temperature of 70° F. Thus, the rh in the insect chamber varied from about 70 to 90%, as the temperature dropped. Resulting recorder traces did not reveal any apparent responses to the combined radiations. Because of these apparent negative results and time limitations, replications were not performed, and no statistical analysis was carried out. Monitoring of the corn borers' CO^ output was used to detect response of the corn borer to frequencies of sound between 5K and 12K Hz. Responses were obtained at several frequencies. Also determined was the effect of temperature change on COg output; a 20% increase occurred for a temperature rise from 76 to 81°. Tests were conducted to determine patterns of respiration resulting from certain biological processes. By confining the insect in a very small chamber and Interconnecting this to the CO^ analyzer with a short length of capillary tubing, an accurate trace of respiration could be obtained. Sev eral traces were obtained during emergence of corn borers. The resulting respiration traces had remarkably similar shapes. A typical trace is shown in Figure 23. Records were also obtained for the diapausing larvae. Fig ure 24 shows a typical portion of the trace. Figure 23. Typical CO^ output of corn borer during emergence Relative CO2 Output o — o bi o ? 3: K) — Figure 24. Typical CO^ output of diapauslng corn borer larvae Relative CO2 Output o N3 3 o w 181 APPENDIX C. REFERENCES BY SUBJECI 182 The European Corn Borer Arbuthnot, K. D. Temperature and precipitation in relation to the number of generations of European corn borer in the United States. U.S. Depart ment of Agriculture Technical Bulletin 987. 1949. Barlow, C. A. Some factors determining the size of infestations of the European corn borer, Ostrinia nubilalis. Canadian Journal of Zoology 41: 963-970. 1963. Barlow, C. A. and Mutchmor, J. A. Some effects of rainfall on the popula tion of the European corn borer, Ostrinia nubilalis (Hbn.) (Pyraustidae: Lepidoptera). Entomologia, Experimentalis et Applicata 6: 21-36. 1963. Beck, S. D., Chippendale, G. M. and Swinton, D. E. Nutrition of the Euro pean corn borer, Ostrinia nubilalis. VI. A larval rearing medium without crude plant fractions. Entomological Society of America, Annals 61; 459- 462. 1968. Bee ton, A. J., George, B. W. and Brindley, T. A. Continuous rearing of European corn borer larvae on artificial medium. Iowa State Journal of Science 37: 163-172. 1962. Chiang, H. C. and Holaway, F. G. Relationships between plant height and yield of field corn as affected by the European corn borer. Journal of Economic Entomology 58: 932-938. 1965. Hanec, W. M. and Laurence, G. A. The biology of the European corn borer, Ostrinia nubilalis (Hubner) in Manitoba. Entomological Society of Manitoba, Proceedings 22; 32, 33. 1967. Harding, J. A., Brindley, T. A. and Dyar, R. C. Survival and development of European corn borers fed gossypol in aritificial diets. Journal of Eco nomic Entomology 60: 1764, 1765. 1967. Hough, W. S. European corn borer in peaches. Journal of Economic Entomol ogy 57: 300-301. 1964. Mutchmor, J. A. Some factors influencing the occurrence and size of the European corn borer, Ostrinia nubilalis. in southwestern Ontario. Canadian Entomologist 91: 798-806. 1959. Youssef, K. H. and Hananad, S. M. The European corn borer, Ostrinia nubilalis Hb., infesting Vicia faba L. in the UAR. Alexandria Journal of Agricultural Research 14: 95-97. 1967. See under Selected References: 6, 21, 29, 30, 61, 71, 84, 86, 87, 95, 108, 113, 145-148, 152, 159, and 160. 183 Insects and Radiation, General Baker, V. H., Wiant, D. E. and Taboada, 0. Effects of electromagnetic energy on plants and animals. Agricultural Engineering 36: 808-812. 1955. Bernhard, C. G., Hoglund, G. and Ottoson, D. On the relation between pig ment position and light sensitivity of the compound eye in different noc turnal insects. Journal of Insect Physiology 9: 573-586. 1963. Burtt, E. T. and Catton, W. T. Is the mosaic theory of insect vision true? 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The use of gamma radiation for the control or eradication of the screw-worm. Journal of Economic Entomology 48: 467-469. 1955. McLeod, D. G. R. and Beck, S. D. Photoperiodic termination of diapause in an insect. Biological Bulletin 124: 84-96. 1963. Miskimen, G. W. Effects of light on mating success and egg-laying activity of the sugarcane borer, Diatraea sacchralis. Entomological Society of America, Annals 59: 280-284. 1966. Picton, H. D. The responses of Drosophila melanogaster to weak electromag netic fields. Unpublished Ph.D. thesis. Evanston, Illinois, Library, Northwestern University. 1964. 184 Ruck, P. Retinal structures and photoreception. Annual Review of Entomol ogy 9: 83-102. 1964. Wellington, W. G. Motor responses evoked by the dorsal ocelli of Sarcophaga aldrichi (Parker) and the orientation of the fly to plane polarized light. Nature 172: 1177-1179. 1953. Wulff, V. J. Physiology of the compound eye. Physiological Review 36: 145-163. 1956. Yeomaiid, A. H. Radiant energy and insects. In Insects, the yearbook of agriculture. Pp. 411-421. Washington, D.C., U.S. Government Printing Office. 1952. See under Selected References: 2, 3, 32, 35, 36, 93, 99, 101-107, 116, 118, 121, 122, 129, and 158. L&. Barr, A., Smith, T. A., Boreham, M. M. and White, K. E. Evaluation of some factors affecting the efficiency of light traps in collecting mosquitoes. Journal of Economic Entomology 56; 123-127. 1963. Bretherton, R. F. Moth traps and their lamps: an attempt at comparative analysis. Entomological Gazette 5: 145-154. 1954. Chapman, J. A. and Kinghorn, J. M. Window flight traps for insects. The Canadian Entomologist 87: 46-47. 1955. Common, I. F. B. A transparent light trap for the field collection of Lepidoptera. Lepidopterists' Society Journal 13: 57-61. 1959. Ficht, G. A. and Hienton, T. E. Control of corn borer by light traps. Agricultural Engineering 20: 144, 152. 1939. Ficht, G. A. and Hienton, T. E. Some of the more important factors govern ing the flight of European corn borer moths to electric traps. Journal of Economic Entomology 34: 599-604. 1941. Frost, S. W. Insects captured in light traps with and without baffles. Canadian Entomologist 90: 566, 567. 1958. Frost, S. W. Insects captured in black-painted and unpainted light traps. Entomological News 70: 54; 55. 1959. Frost, S. W. Response of insects to black and white light. Journal of Economic Entomology 46: 376-377. 1953. 47: 275-278. 1954. Frost, S. W. Traps and lights to catch night-flying insects. Tenth Inter national Congress of Entomology, Proceedings 2: 583-587. 1956. 185 Click, P. A. and Kcllingsworth, J. P. Further studies on the attraction of pink bollworm moths to ultraviolet and visible radiation. Journal of Eco nomic Entomology 49: 158-161. 1956. Click, P. A. and Hollingsworth, J. P. Response of moths of the pink boll- worm and other cotton insects to certain ultraviolet and visible radiation. 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Response of tobacco- and tomato-horn- worm moths to black light. Journal of Economic Entomology 51: 78-80. 1958. Tashiro, H., Hartsock, J. G. and Rohwer, G. G. Development of blacklight traps for European chafer surveys. U.S. Department of Agriculture Techni cal Bulletin 1366. 1967. Tashiro, H. and Tuttle, E. L. Blacklight as an attractant to European chafer bettles. Journal of Economic Entomology 52: 744-746. 1959. Taylor, J. G., Deay, H. 0. and Orem, M. T. Some engineering aspects of electric traps for insects. Agricultural Engineering 32: 496'4&8. 1951.. Webster, A. P. and De Coursey, J. D. The catch curves of insects. Ento mological Society of America, Annals 47: 178-189. 1954. Williams, C- B. Hie influence of moonlight on the activity of certain noc turnal insects, particularly of the family Noctuidae, as indicated by a light trap. Royal Society of London, Philosophical Transactions Series B 226: 357-389. 1936. Williams, C. B. and Davies, L. Simuliidae attracted at night to a trap using ultraviolet light. Nature 179: 924, 925. 1957. See under Selected References: 9, 31, 48, 62, 63, 70, 76, 77, 78, 80, 82, 97, 125, 135, 136, 137, 157, and 174. 187 Insects and Radiation, Laboratory Studies Autrum, H. Electrophysiological analysis of the visual systems in insects. Experimental Cell Research, Supplement 5: 426-439. 1958. Barber, G. W. Observations on the response of adults of European corn borer to light in egg laying. Entomological Society of America, Annals 18: 419-431. 1925. Crescitelli, F. and Jahn, T. L. The electrical response of the dark-adapted grasshopper eye to various intensities of illumination and to different qualities of light. Journal of Cellular and Comparative Physiology 13: 105-112. 1939. Goldsmith, T. H. and Ruck, P. The spectral sensitivities of the dorsal ocelli of cockroaches and honeybees. Journal of General Physiology 41; 1171-1185. 1958. Graham, C. H. and Hartline, K. K. 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See under Selected References: 27, 52, 53, 140, and 151. Insects and Environment Dingle, H. Some factors affecting flight activity in individual milkweed bugs. Journal of Experimental Biology 44: 335-343. 1966. Eddy, G. W., Roth, A. R. and Plapp, F. W., Jr. Studies on the flight hab its of some marked insects. Journal of Economic Entomology 55: 603-607. 1962. Evans, W. G. Notes of the biology and dispersal of Melanophila (Coleoptera: Buprestidae). Pan-Pacific Entomologist 38: 59-62. 1962. Larsen, E. B. The importance of master factors for the activity of noc- tuids. Studies on the activity of insects I. Entomologiske Meddelelser 23: 352-374. 1943. 190 Lewis, T. An analysis of components of wind affecting the accumulation of flying insects near artificial wind-breaks. Applied Biology Annals 55: 365-376. 1966. Lutz, F. E. Wind and the direction of insect flight. American Museum Novitates 291: 1-4. 1927. Richards, A. G. The effect of temperature on wing-beat frequency in the male of the cockroach Periplaneta americana. Entomological News 74:. 91-94. 1963. Starkweather, R. J. and Sullivan, W. N. Insect tolerance to increased atmospheric pressure. Journal of Economic Entomology 57; 766-768. 1964. Uvarov, B. P. Insects and climate. Entomological Society of London, Transactions 79: 1-247. 1931. See under Selected References: 173. Biological Rhythms Brady, J. Control of the circadian rhythm of activity in the cockroach. I. Role of the corpora cardiaca, brain and stress. II. Role of the sub- oesophageal ganglion and ventral nerve cord. Journal of Experimental Biology 47: 153-165, 165-178. 1967. Calhoun, J. B. Twenty-four hour periodicities in the animal kingdom. Ft. 1 invertibrates. Journal of the Tennessee Academy of Science 19: 179-200, 252-262. 1944. Danilevakii, A. S. Photoperiodism and seasonal development of insects. London, England, Oliver and Boyd Ltd. 1965. Dsvis, R. Daily rhythm in flight and development of the corn leaf aphid, Rhopalosiphum maidis. Entomological Society of America, Annals 59: 82-85. 1966. Edwards, D. K. Activity rhythms of lepidopterous defoliators. Canadian Journal of Zoology 42: 923-937. 1964. Ehret, C. F. and Trucco, E. Molecular models for the circadian clock. I. The chronon concept. Journal of Theoretical Biology 15: 240-262. 1967. Fingerman, M., Lago, A. D. and Lowe, M. F. Rhythms of locomotor activity and 02 - consumption of the grasshopper, Roma le a microptera. American Mid land Naturalist 59: 58-66. 1958. Marker, J. E. Diurnal rhythms. Annual Review of Entomology 6: 131-146. 1961. 191 Hairker, J. E. Diurnal rhythms and homeostatic mechanisms. Cambridge, England, University Press. 1964. Harker, J. E, The effect of a biological clock on the development rate of Dr OS ophila pupae. Journal of Experimental Biology 42: 323-337. 1965. Marker, J. E. The effect of photoperiod on the developmental rate of Drosophilia pupae. Journal of Experimental Biology 43: 411-423. 1965. Har-ker, J. E. The physiology of diurnal rhythms. Cambridge, England, Cam bridge University Press. 1964. Hengst, D. The resonance of the emergence rhythmics in Drosophila pseudoobscura. Zeitschrift £ur Vergleichende Physiologie 54: 12-19. 1967. Kinics, C. F. Relationship between serotonin and the circadian rhythm in some nocturnal moths. Nature 214: 386-387. 1967. Keller, E. F. A mathematical description of biological clocks. Currents in Modern Biology 1: 279-284. 1967. Lees, A. D. Photoperiodic timing mechanisms in insects. Nature 210: 986- 989 - 1966. Menlcer, M, and Eskin, A. Circadian clock in photoperiodic time measurement: a test of the Bunning hypothesis. Science 157: 1182-1184. 1967. Mostikov, B. S. and Fukshanskii, L. Ya. Construction of a mathematical model of the 'biological clock' of higher plants. Biophysics 11: 589-596. 1966. Pit tendrigh, C. S. and Minis, D. H. The entrainment of circadian oscilla tions by light and their role as photoperiodic clocks. American Naturalist 98: 261-294. 1964. Reinberg, A. and Ghata, J, Biological rhythms. New York, N.Y., Walker and Co. 1964. Roberts, S. K. "Clock" controlled activity rhythms in the fruit fly. Science 124: 172. 1956. Saunders, D. S. Photoperiodism and time measurement in the parasitic wasp, Nas onia vitripennis. Journal of Insect Physiology 14: 433-450. 1968. Tshernyshev, W. B. Types of 24-hour cycle rhythms of insect activity. Zoologichesii Zhurnal 42: 525-534. 1963. Tyschchenko, V. M. Two-oscillatory model of the physiological mechanism of the photoperiodic reaction of insects. Zhurnal Obshchei Biologii 27: 209- 222. 1966. 192 Wever, R. The duration of re-entrainment of circadian rhythms after phase shifts of the zcxLgcher* A theoretical nivesti^stici*. «Tcurnâl of Thcorsti" cal Biology 13: 187-201. 1966. Wobus, U. The influence of light intensity on the resynchronization of the circadian rhythm of locomotor activity of the cockroach Blaberus craniter Burm. Zeitschrift fur Vergleichende Physiologie 52: 276-289. 1966. See under Selected References: 5, 14, 28, 45, 55, 90, 110, 120, 126, 127, 133, 175, 176 and 179. Measurement of Animal and Plant Respiration Baker, L. E. A rapidly responding narrow-band infrared gaseous CO2 analyzer for physiological studies. IRE Transactions on Bio-Med Electronics BHE-3: 16-24. 1961. Buck, J. Some physical aspects of insect respiration. Annual Review of Entomology 7: 27-56. 1962. Collier, C. R., Affeldt, J. E. and Farr, A. F. Continuous rapid IR CO2 analysis. Journal of Laboratory and Clinical Medicine 45: 526-539. 1955. El-Sharkawy, M. S., Loomis, R. S. and Williams, W. A. Apparent reassimila tion of respiratory carbon dioxide by different plant species. Physiologia Plantarium 20: 171-186. 1967. Hamilton, A. G. Variations in the metabolic rate in male desert locusts. International Congress of Entomology, Proceedings 2: 343-347. 1958. Levengood, W. C. Infrared method for determining circadian patterns of. carbon dioxide release. Zeitschrift fur Vergleich.ende Physiologie 62: 153- 166. 1969. Musgrave, R. B. and Moss, D. N. Photosynthesis under field conditions. I. A portable, closed system for determining net assimilation and respiration of corn. Crop Science 1: 37-41. 1961. Osborn, J. J., Shore, J. H. and Elliott, S. E. A constant-flow valve for respiratory gas sampling. Journal of Applied Physiology 24: 113-114. 1968. Punt, A. The respiration of insects. Physiologia Comparata et Oecologia 2: 59-74. 1949. Robinson, J. R. and Chefurka, W. Continuous measurement of CO2 respired by insects. An ionization chamber method. Analytical Biochemistry 9: 197- 203. 1964. 193 Schneiderman, H. A. and Williams, C. M. An experimental analysis of the discontinuous respiration of the cecrooia silkworm. 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