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Behavioral responses reported for spider mites encountering pyrethroid in secticideson treated plant surfaces have included increased dispersal and cessation of feeding. In our laboratory study, pyrethroid insecticides were applied directly to Banks grass mite, Oligonychus pratensis (Banks), and two spotted spider mite, Tetranychus urticae (Koch), that were then released onto untreated maize, Zea mays L., plants. Initially, a greater proportion of chemically treated mites dispersed compared with untreated mites or those treated with water. Vertical distributions of the two species were similar except after the permethrin treatment. Permethrin inhibited Banks grass mite upward dispersal compared with fenvalerate, water treatments, and controls, whereas two spotted spider mite upward dispersal was not inhibited.

Populations of field-collected Blattella germanica (L.) were placed in one chamber of a modified Ebeling choice box and subjected to selected environmental influences. Relative importance of these influences was determined through analysis of differences in sticky-trap catches which reflected exploratory behavior. Daily trap-catch data were associated with each variable tested. The number of cockroaches caught was found to increase with environmental familiarity, increased temperature, increased number of holes between chambers (especially those located at the bottom of the partition), and food deprivation. Decreased catches resulted from increased cockroach density and fecal contamination.

Secretory-type epithelial cells of the adult female western corn rootworm, Diabrotica virgifera LeConte (Chrysomelidae), apparently responsible for releasing the sex pheromone, are composed of 2 groups of cells. One group is columnar, arranged in a “U” shape, and located dorsally between tergites 7 and 8; the cells of the 2nd group are cuboidal and located ventrally between sternites 7 and 8. Individual cuticular pore openings occur on the 7th abdominal segment and correlate spatially with the epithelial secretory cells.

Adult Tenebrio molitor L. were exposed to 39-MHz radiofrequency (RF) electric fields and examined to determine cytopathological changes in ovarian and testicular tissues. Disintegration of trophocytes and primary oocytes followed by vacuole formation in the germarium and germinal vesicle characterized the effects in ovarian tissue. Condensation of the chromatin material in the follicular epithelial cells was also evident. In testicular tissues, RF treatment caused disintegration of the cyst membranes and spermatocytes and clumping of spermatid nuclei. Mature spermatozoa were not observed in the lumina of the vasa efferentia.

The effects of topically-applied sublethal doses of carbofuran and carbaryl on oviposition and longevity of Diabrotica virgifera LeConte females were studied. At application rates representing very small percentages of their respective LD50 values, females treated with either insecticide oviposited significantly more and lived significantly longer than did control females. Carbofuran enhanced these phenomena more consistently than did carbaryl. No explanations are suggested as to why the carbamate insecticides tested stimulated oviposition and extended longevity.

We developed a rating system to predict the mortality of Diabrotica undecimpunctata howardi Barber larvae used to bioassay soil insecticides. Larvae were categorized, following 48 h exposure to insecticide-treated soil, as living, dead, or in one of five intermediate categories based on movement when exposed to bright light. The eventual mortality of larvae within a rating category was determined by returning the larvae to the treated soil for an additional 5 days and establishing the probability of mortality corresponding to each category. Percentage of dead larvae in the five behavioral rating categories was independent of the insecticide used. Compared to the bioassay method in which the test organisms are considered either alive or dead, the rating system was more consistent and more precise with respect to the assumptions underlying conventional parametric statistics. The rating-system approach is a sensitive and rapid bioassay technique that might be adapted to other test organisms and situations where the subject is under continuous exposure to the toxin being tested.

Aldrin was recommended and used to control the western corn rootworm (Diabrotica virgifera LeConte) (WCR) in Nebraska from 1952 to 1961. During that period, LD50 values for adult WCR tested against aldrin were determined for 19 collection sites in Nebraska. Mean 24 h LD50 values for these sites decreased from 1,539 μg/g in 1962 to 355 μg/g for 1981. A correlation existed between the amount of aldrin used for soil treatments and the aldrin and dieldrin residues, with decreasing LD50 values for the WCR over the observation period.

Scanning electron micrographs and serial longitudinal and cross sections of the western corn rootworm, Diabrotica virgifera LeConte , antennae revealed that the antennal structure of males and females was similar. However, the longer ♂ antennae have more sensilla and possess 6 types of sensilla on the terminal antennal segment not found on the terminal segment of ♀ antennae; the ultimate antennal segment of the female possesses 4 sensillar types not found on the comparable antennal segment of the male.

One- and 3-day-old Tenebrio molitor L. eggs were exposed in special polystyrene holders to radiofrequency (RF) electric fields of different intensities for periods ranging from 2 to 64 seconds. The percent eggs hatched, percent survival of larvae to 10 days, and embryological development were observed following exposure to these RF electric fields. Percent hatch of 1- and 3-day-old T. molitor eggs exposed to RF energy was in general inversely related to the RF energy level. One-day-old eggs were more susceptible than 3-day-old eggs. When the larval stage was attained, interference with normal developmental processes was not apparent. Histological preparations of embryos exposed to RF fields showed that injury to the blastoderm and the germ band depended upon the age of the egg at the time of treatment and indicated that RF treatment adversely affected further embryological development.

German cockroach nymphs ( Blattella germanica (L.)), large milkweed bug nymphs ( Oncopeltus fasciatus (Dall.)) and adult spotted alfalfa aphids ( Therioaphis maculata (Buckton)) were exposed daily for short periods to several areas of the visible spectrum. Daily exposures of cockroaches to light indicated that the longer wave lengths of light may interfere with normal growth. As the daily exposure time was increased, the life span and the mean weights decreased. Daily exposure of the milkweed bugs to the longer wave lengths resulted in an increased maturation period, decreased adult weights, and fewer nymphs reaching the adult stage. Tests with the spotted alfalfa aphid indicated that short daily exposures to the longer wave lengths of light resulted in the birth of fewer nymphs over a period of several months experimentation. Consideration was given to the mechanism responsible for such growth inhibition.

Because it is difficult and time consuming to collect activity data for small insects visually, a recording system using a cage, power source, amplifier, and event recorder was devised to record locomotor activity. The system functions when the test insect makes contact between 2 electrodes placed in the test cage. The system was used to record locomotor activity of Diabrotica virgifera LeConte, Oncopeltus fasciatus (Dallas), and Periplaneta Americana (L.) with different degrees of success, depending upon the conductance (or resistance) of the test insect. Circuit diagrams and operating procedures are presented.

Adults of Diabrotica virgifera LeConte were collected annually from 1963 through 1972 from 18 specific sites in Nebraska and treated with a series of concentrations of diaziuon and phorate to determine annual median lethal dose values. Dosage-mortality curves or regression lines were statistically determined from the annual median lethal dose data. Although the median lethal dose values for both insecticides increased from 1963 to 1972, neither regression line is significant. However, the median lethal dose data for diazinon significantly fit a quadratic curve, indicating possible reversion in susceptibility to diazinon. Predictions of imminent resistance in the field based on the slopes of the regression lines would be speculative.

Approximately 12,000 female Diabrotica virgifera LeConte were extracted with hexane. Part of the resulting extract (oil) was column chromatographed to obtain various ether/hexane fractions. Crude and ether/hexane fractious were bioassayed in the laboratory and in the field. In the laboratory, the 5% ether/hexane fraction was the most attractive; in the field, acetone extracts of the crude hexane extract showed that 500 or more female equivalents were necessary to attract more than 10 males per trap during the testing period.

The activity rhythms of male Blaberus craniifer adults having a small glass ‘window’ implanted in the vertex were studied in contrast to the rhythms of surgical control and untreated cockroaches. Results indicate that entrainment occurred in insects having a ‘window’ in the absence of functional cephalic photoreceptors when exposed to a 12L : 12D photoperiod. Activity rhythms of cockroaches possessing the ‘window’ were comparable to the rhythms of the surgical control and untreated insects.

Adults developing from larvae of the yellow mealworm, Tenebrio molitor L., exposed at sublethal levels to radio-frequency electric fields, exhibited malformed and missing legs. The number of imaginal legs was reduced as exposure time increased. The degree of leg malformation increased when treatment was administered later during the last (sixth) instar. Similar treatments of fifth-instar larvae did not interfere with normal imaginal leg development. Deformities most likely result from heat damage to the histoblasts which project into the legs of the last-instar larvae.

The locomotor activity rhythms of ‘blinded’ Blaberus craniifer adults receiving transplants of either an entire brain or both optic lobes of a donor B. craniifer were studied in contrast to the activity rhythms of surgical control and untreated insects. When the implants were located in the abdomen of a ‘host’ insect beneath a small glass ‘window’ and exposed to a 12L : 12D photoperiod entrainment occurred and the activity of such ‘host’ insects receiving either type of implant was comparable to that of control insects. The results provide some substantiating evidence that locomotor activity rhythms may be controlled by a hormonal clock.

Data obtained from olfactometer tests demonstrated the presence of a sex pheromone in the hexane extract of 5-day-old virgin female face flies, Musca antumnalis De Geer (Diptera: Muscidae). Results of chromatography and simple chemical procedures suggest that the pheromone is an unsaturated hydrocarbon. The sex pheromone of the female face fly probably influences the behavior of the male in 2 ways, by attracting him to the pheromone source and by sexually stimulating him to initiate copulation. Apparently, both visual and olfactory stimuli are involved in the orientation mechanism of the male to the female face fly. The pheromone is perhaps operative over a relatively great distance whereas vision is probably used by pheromonestimulated males for only short-range orientation.

Locomotor activity rhythms of Periplaneta americana (L.) were found to be entrained through the compound eyes and not the ocelli. When the entire head capsule was occluded, the locomotor activity rhythm was random. For those insects having the terminal abdominal sclerites occluded, there was more activity during the photophase than during the scotophase; locomotor activity at the light-to-dark transition was comparable to that of control insects. Transection of the ventral nerve cord did not appear to alter locomotor activity. The involvement of the terminal abdominal ganglion in locomotor activities is considered. Two new low-friction switching methods to record locomotor activity are described.

An inert diatomaceous earth of Arizona origin trade named Perma Guard was evaluated as a grain protectant, insecticidal and pathological properties being studied. Dosage-mortality curves are presented for eight test species confined in wheat dusted with Perma Guard at the rate of 2 to 7 pounds per ton, Ranking in order of decreasing susceptibility these species were: flat grain beetle, Cryptolestes pusillus (Schanherr); rice weevil, Sitophilus oryzae (L.); granary weevil, Sitophilus granarius (L.); lesser grain borer, Rhyzopertha dominica (F.); saw-toothed grain beetle, Oryzaephilus surinamensis (L.); dermestid larva, Trogoderma parabile Beal; red flour beetle, Tribolium castaneum (Herbst); and confused flour beetle, T. confusum Jacquelin du Val. Only the flat grain beetle mortality attained standards of commercial kill during the two weeks' exposure period at the commercially recommended dosage (4 pounds per ton) or below. Mortality exceeded 95% at 5 and 6 pounds per ton for this species. At the peak dosages used, the mortality of the remaining species did not approach the criterion for commercial kill, The results indicate that of the two moisture levels (12% and 14%) of wheat used in this study, the lower level contributed to mortality in both weevil species, the lesser grain borer and the saw-toothed grain beetle. The dust was directly applied to five test species. Significant differences in losses in weight were observed between test and control groups for the lesser grain borer, the confused flour beetle and the red flour beetle. Overall differences in losses in weight between test and control lots of rice and granary weevils were not significant. A drastic difference between test and control first-day mortality in the rice weevil may be indicative of an unknown lethal factor in the dust. The significant differences in loss in weight were ascribed to the dust's abrasive action on the water barrier portion of the epicuticle. The toxicology of this diatomaceous dust was studied. Dissections, epicuticular staining. and histological sectioning showed little that could be construed ns epicuticular damage.

Abdominal photosensitivity in the terminal ganglion of P. americana (L.) was first indicated after studying the phototactic activity of cockroaches whose head capsules were painted with opaque enamel. Following dark adaptation, excised abdominal nerve tissue responded to brief light stimuli of varying duration. Discharge activity was obtained from the ventral nerve cord connectives and was directly related to stimulus duration. Ganglia not darkadapted were unresponsive.

Various portions of the antennae, mouth parts, and legs were painted with shellac to inactivate possible hygroreceptive areas thereon, and the times required by the insects to locate water following these various treatments were recorded. Through a process of elimination the distal part of the fourth antennal segment was found chiefly responsible for hygroreception. Supporting evidence for this was obtained through use of an olfactometer. Sections through the antennae showed considerably more nervous tissue in the fourth segment than in the others.

The relative transmittance of visible and infrared radiation was measured for cuticle from the vertex, 2 pairs of wing tips in repose plus underlying tergite, light and dark pigmented pronotal areas, one wing tip, and the 6th abdominal tergite and sternite of the cockroach, Blaberus craniifer Burmeister. Significant differences in transmission between these cuticular areas, measured in μw/cm2, were observed with the light pigmented pronotal cuticle having the highest and the dark pigmented pronotal cuticle having the lowest percent transmittance at all wave lengths.

When larvae and adults of Tenebrio molitor L. were exposed at sublethal levels to 39-MHz radiofrequency (RF) electric fields, the RF treatment of last-stage larvae and adults reduced female fecundity. The reduction fecundity was more pronounced with longer periods of exposure and higher electrode voltages. The effect of RF energy on fecundity was more dependent upon treatment of males than upon treatment of females. Exposure of larval stages to RF energy resulted in a reduction in both the size of the ovaries and the number of eggs which developed in females that emerged from treated larvae.

The sequence of mating behavior for virgin western corn rootworms, Diabrotica virgifera LeConte, included the following behavioral categories: preliminary courtship and mounting; physical stimulation of the female by the male; and copulation. Various tactile stimuli, including antennal palpitation and stroking activities involving the mesothoracic legs, were performed by the male during the mating process.

Starting in 1963 adults of the western corn rootworm, Diabrotica virgifera Le Conte, were collected annually from 18 sites in Nebraska and treated to determine LD30 levels for diazinon and phorate. Dosage-mortality curves and LD30 values are presented for both insecticides for 1963 through 1967. The LD30 values for both diazinon and phorate have increased significantly since 1963. Control of the western corn rootworm with both insecticides remains effective, but the increasing LD30 values should alert entomologists to possible failures in the field.

Twenty-nine insecticidal compounds were assayed for their toxicity to the western corn rootworm, D. virgifera LeConte. The toxicants included 13 carbamates, 13 organophosphates, and 3 chlorinated hydrocarbons. LD50 values in µg/g are presented for all the compounds tested for the years 1963–68. Seven of the 10 most toxic insecticides were carbamates, and 3 were organophosphates.

The relative resistance of the western corn rootworm, Diabrotica rirgifera LeConte to aldrin and diazinon was determined for adults collected from 18 sites in Nebraska and from several sites in adjacent States. The LD50 values in micrograms/gram of insect were determined by topical application for all collection sites. The results indicate a wide range in susceptibility for insects collected in Nebraska. By comparison with the LD60 values of Nebraska-collected insects, it would appear that control problems might occur ill some of the surrounding States in the near future.

Forty-eight species of cultivated and wild flowering plants in Nebraska were assayed for juvenile hormone (JH) activity. Except for a few plant species, extracts were made of flower heads. Extracts were assayed using pupae of the yellow mealworm, Tenebrio molitor L., as test indicators of JH activity. Examination of over 900 T. molitor adults, treated as pupae, revealed limited evidence of juvenilization. Vestigial urogomphi were present on some adults previously treated as pupae with extracts of 5 plant species. Bioassay of Nepeta cataria (Tourn.) Reichenb, extracts revealed 1 pupal-adult intermediate.

Adult O. fasciatus (Dall.) were exposed in boxes offering a two-choice situation between various wave lengths in the visible spectrum. Opaque and clear exposures were similarly tested. In any given color combination, more insects chose the shorter wave length. These results are interesting because in general the longer wave lengths are more deleterious in nature than the shorter wave lengths. The location of photoreceptors other than ocelli and compound eyes is speculated upon.

Adults of the western corn rootworm. Diabrotica virgifera LeConte, collected from two widely separated areas in Nebraska, were assayed for susceptibility to aldrin, Diazinon® ( O,O -diethyl O -(2-isopropyl-4-methyl-6-pyrimidinyl) phosphorothioate), and heptachlor. Dosage-mortality curves and LD50 values were determined for each insecticide. Results indicated that adults of D. virgifera collected from the central part of the State required about 100 times as much aldrin or heptachlor per insect to produce an LD50in 2 hours as adults collected in eastern Nebraska. LD50 values for Diazinon tested on beetles from the two areas were virtually the same. The reasons for such differential resistance are considered.

Small pieces of cuticle were removed from the following areas of the cockroach, P. americana , to determine the relative transmittance qualities across the visible and infrared regions of the spectrum: wing tip; abdominal tergite and sternite; light and dark pigmented areas of the pronotum; vertex; two pairs of wing tips plus underlying tergite. The transmittance across the spectral areas investigated showed significant differences in μW/cm 2 between the cuticular areas assayed. A single wing tip possessed high transmittance qualities whereas the vertex and lesser pigmented cuticle showed considerably lower per cent transmission.

A well-defined sexual attraction exists between mature virgin female and mature unmated male face flies, Musca autumnalis , tested in a Y-tube olfactometer. Attraction seems to be maximum when females are 5 to 6 days old and males are 4 to 8 days old post emergence. Gonadotrophic cycles probably play a role in the periodicity of the sexual attraction. Attraction as well as insemination reach a peak during the noon hours, gradually decline through the afternoon, and reach a minimum level in the evening. A daily rhythm of sex pheromone release and/or production is most probably present in virgin female flies.

Ovarian development and mating in the face fly, Musca autumnalis , was correlated with the nutritional factors present in the adult diet. A proteinaceous diet appeared to be indispensable to the female face fly for normal ovarian development and increased mating activity. It is probable that lack of protein in the adult diet not only affected ovarian development but also influenced the activity of the corpora allata, thereby indirectly affecting sex pheromone production and/or release and ultimately resulted in decreased mating activity.

During the last three to four decades, numerous insect species have been exposed to a series of new and more toxic insecticides. After many years of exposure to certain insecticides in the field, assays of some insect populations now show decreased susceptibility to those toxicants. The response of insects to the continued exposure to various insecticides has resulted in a phenomenon well known to all entomologists as insecticide “resistance.” Resistance, according to Crow (1957), designates a genetic change which is a response to pesticide selection.

Reproduction of the red flour beetle, Tribolium castaneum (Herbst), was lower on whole grain than has been reported on milled grain in earlier studies. Generally, fecundity increased with increasing temperature (20-32°C) and moisture (10-16%). However, interaction of adult survival and fecundity caused net reproduction to peak at 27°C and 16% moisture. This resulted from greater adult survival with increasing moisture, but decreasing survival with increasing temperature.

Adults of Diabrolica virgifera LeConte were placed in choice boxes whose tops consisted of filters of six different wavelengths ranging from ultraviolet to red. Observations to determine the most attractive wavelengths, made five times daily, indicated that wavelengths in the yellow spectral region were significantly more attractive than those in the red region; additionally, red was more attractive than other wavelengths tested. The use of colored traps for assessing field populations of adult western corn rootworms is indicated.

A technique to obtain objective mortality data for larvae of the western corn rootworm treated with diazinon, Bux® [ m- (l-ethylpropyl) phenyl methylcarbamate mixture with m- (l-methylbutyl) phenyl methylcarbamate], and phorate is detailed. The use of negative phototactic larval activity following insecticide treatment was more consistant than determining death by observation. For diazinon, the percentage differences in LD50 values between larvae and adults (phototactic technique) for 1974 was 1.04. Differences in LD50 values (observation) between larvae and adults for 1962 and 1969 were 51.6 and 17.0, respectively.

A portable collecting device constructed from a 3-inch mailing tube, a 1-pint ice cream container, and a 1-pint metal funnel using a hand vacuum cleaner powered by a portable generator has been used to collect more than 25,000 adults of the northern corn rootworm, Diabrotica longicornis (Say), the western corn rootworm, Diabrotica virgifera LeConte, and the spotted cucumber beetle, Diabrotica undecimpunctata howardi Barber. The device can be used either to collect insects directly or trap them for transfer to larger cages.

The effects of photoperiod on various biological phenomena in insects are well known. Relationships between photoperiod and behavior, reproduction, adult emergence, metabolism, diapause, and numerous other factors are receiving considerable attention. The reason for such studies is to better explain the response of an insect to its environment as related to light. Because photoperiod has significant effects on various life processes in insects, this study was undertaken to determine what effect photoperiod might play in regulating oviposition in the western corn rootworm, Diabrotica virgifera LeConte.

Adult Diabrotica virgifera LeConte were topically treated with a series of dosages of diazinon at 3-hour intervals throughout a 24-hour photoperiod in 1967 and 1968. Results indicate that the LD50 values vary during a 24-hour period, resulting in a sensitivity rhythm dependent upon time of treatment during the photoperiod. The data indicate the desirability of conducting bioassays during specific time periods of a 24-hour photoperiod.

Western corn rootworm adults were collected between 18 July and 4 Aug. from corn at 19 geographical sites throughout Nebraska and returned to the laboratory in Lincoln for testing. Mean weights for beetles from each collection site were determined prior to treatment. Unsexed beetles were individually treated by topical application of 1 ul of an acetone solution of the test insecticides to the posterior ventral abdominal area. Beetles were anesthesized with CO2 before treatment. Treatment solutions were prepared with reagent grade acetone using technical grade insecticides. Six to eight dosages, plus an acetone check, were used to determine 2-h LD50 values for all insecticides from all collection sites; two replicates of 10 insects each were used for each dosage rate tested. Insects were declared dead if they could not regain their footing 2 h posttreatment. Dosage-mortality data were calculated in ug/g of insect weight using a probit analysis FORTRAN computer program.

Western corn rootworm adults were collected between Jul 12 and Aug 5 from corn at 19 geographical sites throughout Nebraska and returned to the laboratory in Lincoln for testing. Mean weights for beetles from each collection site were determined prior to treatment. Unsexed beetles were individually treated by topical application of 1 ul of an acetone solution of the test insecticides to the posterior ventral abdominal area. Beetles were anesthesized with CO2prior to treatment. Treatment solutions were prepared with reagent grade acetone using technical grade insecticides. Six to 8 dosages, plus an acetone check, were used to determine 2-h LD50values for all insecticides from all collection sites; 2 replicates of 10 insects each were used for each dosage rate tested, insects were declared dead if they could not regain their footing 2-h post treatment. Dosage-mortality data were calculated in ug/g of insect weight using probit analysis FORTRAN computer program.

Western corn rootworm beetles were collected between Jul 13 and Aug 6 from corn at 19 geographical sites throughout NE and returned to the laboratory in Lincoln for testing. Mean weights for beetles from each collection site were determined prior to tretment. Unsexed beetles were individually treated by topical application of 1 ml of an acetone solution of the test insecticides to the posterior ventral abdominal area. Beetles were anesthesized with CO2 prior to treatment. Treatment solutions were prepared with reagent grade acetone using technical grade insecticides. Six to eignt dosages, plus an acetone check, were used to determine 2 hr LD50. values for all insecticides from all collection sites; 2 replicates of 10 insects each were used for each dosage rate tested. Insects were declared dead if they could not regain their footing 2 hr post-treatment. Dosage-mortality data were calculated in mg/g of insect weight using a FORTRAN computer program.