Annals of the Entomological Society of America

When 2- to 3-day-old male Musca domestica L. (Diptera: Muscidae) were injected with 20 µg of 1,3 propanediol dimethanesulfonate, most sperm had dominant lethal mutations so the males were sterile in the initial matings. Testes sectioned at regular intervals postinjection contained damaged meiotic and premeiotic cells; pycnotic nuclei were observed 1 day postinjection; and spermatocytes with chromosomal bridges and fragments were observed the 2nd and 3rd day postinjection. Also, the testes contained few spermatocytes the 4th and 5th day postinjection, thus spermatids were scarce the 5th and 7th day. However, sperm production was never completely interrupted, and the level of spermatogenesis 11-13 days postinjection was returning to normal levels. Incontrast, when males were treated with 3 kR of x-rays, all sperm contained dominant lethal mutations, all gonialcells were killed, and the spermatogenic cycle ceased. Males that mated repeatedly after treatment with the chemosterilant recovered their fertility and became as fertile as the controls after 7-8 matings, but the males that did not remate repeatedly did not recover fertility. There was little difference between fertility of males mated 1, 7, or 12 days posttreatment if they remained celibate in the interim. Irradiated males were able to transfer sperm for many matings over several weeks.

Adults, nymphs, and larvae of Argas (Persicargas) abdussalami, new species, are described from the environs of Lahore, Pakistan. These ticks were found on limbs of trees in which the White-backed Vulture, Gyps (=Pseudogyps) bengalensis (Gmelin), and other wild birds nest, as well as on walls of buildings where pigeons nest. A single collection was taken from a domestic chicken pen; only A. (P.) persicus, however, was present in all other lots associated with domestic chicken in this area. This species differs distinctly in each developmental stage from A. (P.) persicus (Oken), as well as from A. (P.) arboreus Kaiser, Hoogstraal, and Kohls, of northern and southern Africa, and from A. (P.) beklemischevi Pospelova-Shtrom, Vassilieva, and Semaschko, of Turkmenia SSR. Unpublished data suggest the significant role of this group of ticks as reservoirs and vectors of certain arboviruses infecting humans and birds.

Quantitative determinations of the response thresholds of male moths exposed to ether extracts of female abdomen tips provided evidence for the behaviorally similar nature of female sex pheromones between Trichoplusia ni (Hübner) and Autographa californica (Speyer) and between Heliothis sea (Boddie) and H. virescens (F.). Males of A. californica attempted to mate with females of T. ni, without successful coupling occurring. Certain males of H. zea that succeeded in coupling with females of H. virescens could neither transfer spermatophores nor separate from the females. No successful interspecific transfer of a spermatophore occurred among any of the species, indicating the existence of morphological or physiological reproductive isolating mechanisms other than the female sex pheromone.

The chromosome complements of 2 argasid ticks, Ornithodoros (Pavlovskyella) macmillani Hoogstraal and Kohls and O. (P.) gurneyi Warburton, are described and compared with 5 other chromosomally known species of the subgenus. Four of these 7 species have a 2n number of 16, but O. gurneyi has a diploid number of 12 chromosomes, the lowest number yet reported for any species of tick. The 2 species used in this study are the only ones in the genus Ornithodoros known to be restricted to Australia.

The number, gross morphology, and size of the chromosomes were determined for 3 species of dermanyssid mites. Early embryonic somatic tissue was studied using the aceto-orecin or aceto-carmine squash technique. Dermanyssits gallinae (De Geer), the chicken mite, had a haploid number of 3 and a diploid number of 6 chromosomes. The 2 isobrachial chromosomes were approximately 7.0 and 6.8μ and the heterobrachial one was about 5.4μ long. One secondary constriction was observed and it was situated on the short arm of the heterobrachial chromosome. The 2 macronyssine species had smaller, but a greater number of chromosomes than did D. gallinae. Ornithonyssus sylviarum (Canestrini & Fanzago), the northern fowl mite, had haploid and diploid numbers, respectively, of 9 and 18 cephalobrachial (or diffusecentric) chromosomes and these were 1.0 and 1.8μ long. The tropical rat mite, Ornithonyssus bacoti (Hirst), had haploid and diploid chromosome numbers of 8 and i6, respectively, and the chromosomes were 1.9 to 3.7μ long. Seven of these appeared to be cephalobrachial (or diffusecentric), whereas the eighth appeared isobrachial (or diffusecentric) and was approximately twice the length of the shortest chromosome. It is not certain that the 2 macronyssine species have monocentric chromosomes since no centromeres were seen, therefore the designations of cephalo- and isobrachial chromosomes are made tentatively in O. sylviarum and O. bacoti. Close agreement between the results of rearing experiments and of chromosome analyses of eggs indicated that sex determination in the 3 species was of the haplo-diploid type. Virgin females, in the 2 macronyssine species, laid only haploid eggs and produced male offspring only. Virgin female D. gallinae did not oviposit. Mated females of all 3 species laid haploid and diploid eggs in a 1:1 ratio and produced progeny of both sexes. It was suggested that D. gallinae and the macronyssine species might not be confamilial.

A new species of Ixodes having some morphological features suggestive of Haemaphysalis is described from 1 nymph (holotype) and 3 larvae from Scapteromys tumidus, 1 larva from Akodon obscurus, and 1 larva from Oryzomys flavescens. The new species differs so markedly from all other species of Ixodes that a new subgenus, Haemixodes, is proposed.

This study was conducted to elucidate some of the behavioral patterns of Macrocheles muscaedomesticae (Scopoli), a predator of the house fly, Musca domestica L. Scanning electron micrographs of the tips of tarsi I show at least 8 sensory-rod type of setae that are apparently involved in odor perception. It appears that a water-soluble chemical or chemicals on the body surface of male and female house flies may incite the mite to attach. In addition to being phoretic on the house fly, the mite is capable of doing bodily harm, apparently by biting through the intersegmental membranes of the adult fly. Phoresy is influenced by such factors as temperature, developmental stages of the mites, chemical stimuli, and density of mites and flies. Given a choice, mites preferred the odor of the adult house fly over fly eggs. The mites were also quite sensitive to the odor of ammonia and skatole and responded positively to low concentrations of these compounds.

Detailed descriptions, illustrations, host and distributional data, and a key to the larvae of 28 species and 1 subspecies of Ornithodorinae of the Eastern Hemisphere are given. Also, the cosmopolitan Ornithodoros capensis Neumann and Otobius megnini (Dugès) as well as the Eastern Hemisphere subgenera of Argas are included in the key.

Fusura civica, new genus and species, is of unusual interest because it is associated with the guano of Steatonis caripensis, a bird implicated in the epidemiology of histoplasmosis.

Leiodinychus krameri (G. and R. Canestrini) was reared in the laboratory under various conditions of temperature and relative humidity, on what appeared to be an excellent diet. Survival and developmental rates under these conditions are evaluated. Rearing to the adult stage was achieved only at a temperature range from 20° to 30°C, and humidities of 80% or 95%; no eggs hatched in 50% RH. Comparison of adult sizes of mites reared at 30° and 95% with those reared at 20° and 95% shows that the increased rate of development at the higher temperature was accompanied by a smaller body size. Physiological explanations are offered, and optimum temperature is discussed. L. krameri was found to have a wide range of adaptability and a correspondingly high survival potential.

Detailed descriptions, illustrations, and data on hosts and distribution of 28 species in 3 genera, as well as a key to the larval Argasidae of the Western Hemisphere, are given. Described as new are Ornithodoros denmarki, taken on or in association with sea birds in Florida; Jamaica; Trinidad; Raza and Calaveras Islands in Gulf of Baja. California, Mexico; and Rabbit Island near Oahu, Hawaii; (). rossi from a long-nosed bat, Leptonycteris nivalis (type host), Pima County, Arizona, and a big brown bat, Eptesicus fuscus, Santa Cruz County, Arizona, and from the leaf-nosed bat, Macrotus californicus, Sinaloa and Baja California del Sur, Mexico; O. elongatus from a crate containing papaya fruit and iguana lizards sent from the Dominican Republic to Miami, Florida, USA. O. dugesi Mazzotti and O. aquilae Cooley are reduced to synonyms of O. talaje (Guérin-Méneville) and O. concanensis Cooley and Kohls, respectively.

Mating, fertilization, reproduction, ovoviviparity, and oviposition of Leiodinychus krameri (G. and R. Canestrini) are discussed. Mating is described in 3 phases: (1) the premating or exploratory phase, (2) formation of the sperm packet and its attachment to the female, and (3) assimilation of the sperm packet by the female, and post mating behavior. Several case histories illustrating un-usual procedures are discussed, as is competition between the sexes.

The effect of amputations of the palps and tarsi I on the sensory behavior of Macrocheles muscaedomesticae (Scopoli), a mite which is predaceous on house fly, Musca domestica L., eggs and phoretic on adult house flies, was determined. With tarsi I removed, the mites did not attach to house flies and were not attracted to the adults, eggs, or pupae of house flies. With the palps removed, the mites were less mobile than normal, but responded normally to a repellent. It was demonstrated that the palps touch the substrate alternately when the mite is walking. It was concluded that receptors of olfactory stimuli are on tarsi I and receptors of contact stimuli are on the palps.

In the laboratory, both larvae and nymphs of Dermacentor variabilis (Say) fed most readily on meadow voles, Microtus pennsylvanicus (Ord), and less readily on white-footed mice, Peromyscus leucopus (Rafinesque), and on Norway rats. No relationships were found between (1) the proportion of subadult ticks which fed on a host and the total number of such ticks exposed to hosts in exposure groups which ranged from a single larva or nymph to 100 larvae or nymphs per host animal, (2) the duration of larval or nymphal engorgement and the numbers of subadult ticks to which the host was exposed, or (3) the numbers of ticks attaching to a host and the body size of the host. The subadult feeding rates for each host and the duration of feeding for each, stage were used as bases for comparing the contribution of the several small-mammal hosts of this tick, as well as for determining differences in subadult tick density between different vegetative types and between different years.

Uropodid mites are generally considered to be fungus-feeders (Hughes 1959). However, Rhode (1959) found Fuscuropoda vegetans (De Geer) [=Fuscuropoda marginata (Koch) according to Ryke (1958)] to be a predator of Caloglyphus mycophagus (Megnin) (Acarina: Acaridae). Axtell (1963a) reported that uropodid mites occurred frequently in samples of manure of dairy cattle and chickens collected from inside barns in New York State. The immature stages of the house fly, Musca domestica L., occur frequently in manure, suggesting the possibility that certain uropodids are predaceous on eggs and first-instar larvae of the house fly. Axtell (1961)

Field data obtained during 1963–65 on a study area near Montpelier, Virginia, were used in an investigation of relationships between solar radiation and air temperature and activity of Dermacentor variabilis (Say) adults and subadults. Analysis of the data by statistical methods indicated that there is a real relationship between solar radiation received per day and daily activity of larvae (but not of nymphs) during the period of spring feeding. Continuous larval activity occurred during the periods when an average daily solar radiation level of 200 langleys or more was received in the tick habitat. A real relationship was found also between solar radiation levels and daily questing activity of adults; continuous adult activity occurred during the periods when the daylight period exceeded 13 hours and an average daily solar radiation level of about 300 langleys was received in the habitat. No relationship was found between tick activity and air temperature.

The occurrence of uricose glands in the male reproductive system appears to be unique for the Blattaria. These glands are present only in the Blaberoidea, and may have arisen in the plectopterine-blatteline, and the blaberid stocks. The glands are relatively common among the Plectopterinae, occur less frequently in the Blattellinae, and are rare (relics) in a few Blaberidae (Epilamprinae). It is suggested that uric acid, when poured over the spermatophore, may have served to protect the spermatophore from being eaten by the female herself, or by other insects.

Stimulation to oviposit and loss of receptivity to males by female Musca domestica L. (Diptera: Muscidae) are caused by the presence in the female of the accessory material produced in the male ejaculatory duct. Lesser amounts of the material can induce oviposition without loss of receptivity, and the effect of the material on both activities is apparently somewhat quantitative. Females mating early, shortly after they became sexually receptive, recovered receptivity in time more often than females that mated after they reached full maturity. Also, newly receptive females allowed to mate with males having a limited quantity of accessory material and then allowed to oviposit over an extended period showed significantly more remating than females that were not allowed to oviposit.

Fifty adult Coleomegilla maculata (De Geer) were fed on 250 ml of an aqueous solution of sodium acetate-1-C14 which contained 600 micrograms of the salt; total C14 was 10 microcuries. After 4 hr, the beetles were homogenized, the amino acids were extracted and separated by thin-layer chromatography, and the activity was measured, using a scintillation counter. Glycine, serine, aspartic acid, glutamic acid, proline, and lysine showed high activity, and are considered to have been synthesized in vivo. They are apparently nonessential, in contrast to threonine, phenylalanine, isoleucine, and valine, which are essential or derived exclusively from essential dietary constituents. The low activity shown by alanine, leucine, arginine, and histidine indicated a low level of C14 incorporation. Three unknown ninhydrin-positive compounds were isolated, in addition to the 19 amino acids that were identified.

Radiation-induced mortality was investigated for developmental stages of house crickets, Acheta domesticus (L.), and yellow mealworms, Tenebrio molitor L. Insects were exposed to gamma rays from a 60Co source at rates of 3 or 30 kiloroentgens (kr) per minute and given total exposures of 1–512 kr in 100% increments. Postirradiation temperature was 28°C. Effects were expressed as differences in mean and median life expectancy. In general there was a decline in radiosensitivity with age, although there were exceptions. Acheta was unusually radiosensitive, with life expectancy of all stages severely shortened by exposure to 4 kr. Tenebrio pupae and adults exhibited a survival plateau, with similar life expectancies following exposures from 8 to 32 or 64 kr. Some increase in life expectancy appeared following low exposure doses of radiation.

Changes in the free and peptide-bound amino acids during the 3rd and 4th larval instars and the pupal stage of Aedes aegypti (L.) (Diptera: Culicidae) were studied. Thirty-six ninhydrin-positive compounds were separated on chromatograms of deproteinized insect extracts. Glutamic acid, alanine, tyrosine, and arginine consistently occurred in high concentration among the free amino acids, whereas among the peptide-bound amino acids, glutamic and aspartic acids and glycine were the principal components. In spite of various fluctuations, no definite developmental patterns emerged from the study, and no specific correlation of amino acid changes with development was possible. The possible significance of several of the changes are discussed. Several nonprotein amino derivatives were also present. The occurrence of citrulline and urea during only the larval stage suggested that urea may be an important excretory product during this stage.

Beginning at hatching, larvae of the Colorado potato beetle, Leptinotarsa decemlineata (Say), were fed young, bloom-stage, and senescent foliage of 4 solanaceous plants, namely, potato, eggplant, horse-nettle, and 4 varieties of tomato. Under laboratory rearing conditions, larvae completed their growth most rapidly on young foliage of potato, while larval stadia were prolonged for those fed some of the other plants, especially the senescent plants. Percent survival from first-instar larvae to adults was relatively high for all that had fed on the potato foliages, young eggplant, and bloom-stage Rutgers tomato, but was extremely low for those fed senescent foliage of the tomato varieties. Average adult weights were higher for those that had fed as larvae on foliages of potato and bloom-stage Rutgers tomato, lowest for those reared on young eggplant foliages. Ethanol extracts were made of the several kinds of foliages, and the free amino acid composition of the extracts was checked by 1- and 2-way paper chromatography. Extracts of young potato foliage contained the greatest variety of amino acids, and all potato foliages contained all the essential amino acids. Threonine and tryptophan were absent from other extracts. The most prominent amino acids and amides in all the plant extracts were glutamic acid, serine, aspartic acid, alanine, glutamine, and gamma aminobutyric acid.

Fatty acid composition was determined in various developmental stages of two strains of Anopheles freeborni Aitken, one from the State of Washington (47° N lat.) and one from California (37° N). Tentative identification was based on similar emission peaks from gas chromatograms of test materials and authentic samples. Palmitic, palmitoleic, and oleic acids collectively comprised at least 70% of total fatty acid. In both strains, aged females with identical temperature experience on short photoperiod had 11%–15% greater levels of principal unsaturated fatty acids than did females on long photoperiod conditions. Though differences in level were noted between sexes and various growth stages of the 2 strains, there was marked similarity between short photoperiod females of both strains maintained on sucrose for 10 days.

When electrophysiological techniques were used to determine the acoustic sensitivity of Ostrinia nubilalis (Hübner) (Lepidoptera: Pyraustidae) moths, the tympanic organ was found to be served by 2 acoustic (A) cells, one about 20 decibels (db) more sensitive than the other, and by 1 nonacoustic (B) cell with a spike rate of 50–100 per sec. The tympanic organ detected frequencies of 14–100 kilohertz (kHz) at 90 and 75 db, respectively, but the moths were most sensitive to frequencies of 25 and 60 kHz and slightly less sensitive to those between. Pulse trains of 25-kHz frequencies caused more moths to show the avoidance response than trains of 20, 30, or 50 kHz at sound levels of 80–90 db at 1 meter.

Electrophysiological investigation of the action of 20 phenyl carbamates in Periplaneta americana (L.) has shown that the most active compounds readily penetrate into the ganglia, facilitating neurone discharge and causing rapid and reversible synaptic block. The relative effectiveness of the individual compounds in producing this neurophysiological response is almost exactly that found for the inhibition of cholinesterase, and demonstrates dependence upon stereochemical features corresponding to those of acetyl choline. The neurophysiological effects produced by the individual carbamatos were similar to those produced by dimethyl p-nitrophenyl phosphate but differed both qualitatively and quantitatively from those produced by nicotine. The method used in this study provides a convenient biological assay technique for toxicological evaluation at the neurone level.

High population densities of 2 dytiscid beetles, Laccophilus fasciatus Aubé and L. maculosus Say, occur in some waste-oxidation lagoons in Missouri. These lagoons provide optimal conditions for reproduction to certain dipterous pests, notably mosquitoes and midges. In laboratory studies, adults of both dytiscid species were very active and voracious predators on the immature stages (especially the younger instars) of Culex pipiens L., and Glyptotendipes barbipes (Staeger). Mosquito pupae were less often attacked than larvae. G. barbipes were subject to predation before and during tube construction, when larvae left the tubes, and, as pupae, when they migrated to the water surface for adult emergence. The 2 Laccophilus species differed little in their predaceous capacities, and no difference was found between the sexes of either. Predation occurred to some extent under greatly reduced illumination.

The superficial probing behavior of the pea aphid, Acyrthosiphon pisum (Harris), was electronically monitored and studied to determine its relationship to the transmission of a stylet-borne virus (bean yellow mosaic virus (BYMV)). Voltage fluctuations which accompanied salivation were amplified and recorded on stripcharts, and the charts were examined to determine if a specific waveform could be correlated with either the acquisition or inoculation of BYMV by the aphids. A distinctive waveform was found to be associated with the acquisition of BYMV in 91.8% of the successful transmissions. A hypothesis is presented to explain how aphids acquire virus during superficial probes into infected plants. No significant correlations could be found between any waveform and the inoculation of BYMV.

Laboratory mating activities were analyzed in wild and colonized forms of Culex nigripalpus Theobald. Mating experiments utilizing colony females produced insemination levels of about 75% whereas in those experiments involving wild females the insemination rates were less than 2%. Mating success was independent of the type of male used in each cross. Wild genetic material was rapidly incorporated into colony strains via wild males crossed to colony females. This method was used to establish a laboratory marker strain which contains the mutant form, orange fat color.

Aedes albopictus (Skuse) (Diptera: Culicidae), the Asian tiger mosquito indigenous to Asia, now an invasive species worldwide, is an important vector for several arboviruses. Genetic analysis using the mitochondrial nicotinamide adenine dinucleotide dehydrogenase subunit 5 (ND5) gene was carried out in populations from Cameroon (n = 50), Hawaii (n = 38), Italy (n = 20), the continental United States, Brazil, and its native range. Data for Brazil, the continental United States, and the native range was obtained from Birungi and Munstermann (2002). Direct sequencing was used to identity unique haplotypes. The limited phylogeographic partitioning of haplotypes with low levels of sequence divergence in both Cameroon and Hawaii was consistent with the population structure of Ae. albopictus in the United States and Brazil. Four new haplotypes were identified from the samples from Cameroon and Hawaii, adding to previously described haplotypes. Hawaii shared a haplotype with Cameroon that was unique to these two regions. Hawaii also had higher overall haplotype diversity than seen in previous continental United States, Brazil, or native range populations. Hawaiian, Cameroon, and Italian populations did not share haplotypes with Brazil, which validates the earlier mitochondrial DNA studies indicating a separate introduction of this species into Brazil.

The concealed mesothoracic spiracles of adult Scarabaeoidea have the same types of immobile filter apparatusas abdominal spiracles but usually differ in having amedial extension of the peritreme and have a different type of closing device. Associated with the mesothoracic spiracles are 1 or more setiferous intersegmentalia. Meta thoracic spiracles are simple in structure, have movablelips, and are unlike either mesothoracic or abdominal spiracles. Evolutionary trends found in mesothoracic spiracles are the development of a porous or solid filter apparatus from separate atrial spines, a reduction in the size of the spiracular opening, and a reduction in the number of intersegmentalia from several on each side to a median, setiferous sclerite. Many of the structures found in both mesothoracic spiracles and intersegmentalia appear to have taxonomic value. The degree of specialization found in both mesothoracic and abdominal spiracles and in adjacent structures is summarized. Pleocoma and the Lucanidae are the least specialized Scarabaeoidea; other less specialized groups are Passalidae, Troginae, Geotrupinae, Taurocerastinae, Oncerinae (Oncerus), Acoma, Podolasia, Glaphyrinae, Acanthocerinae, Ochodaeinae, and Allidostominae. Melolonthinae, Dynastinae, Rutelinae, and Cetoniinae are the most specialized groups.

The digestive tract of Cardiochiles nigriceps Viereck consists of a narrow esophagus, a large thin-walled crop, the proventriculus. and an active epithelium present in the ventriculus. The malpighian tubules are free in the body cavity and are relatively short. The hindgut is divided into 2 distinct regions with rectal pads in the posterior section. The female internal reproductive system consists of 2 pairs of elongated ovarioles. The proximal portion of the egg tube is enlarged and contains 20–30 mature ova. The calyx also is enlarged and filled with a fluid in which several ova may be embedded. Two prominent accessory glands and a small spermatheca are present. The male internal reproductive system consists of 2 testes each containing 1 sperm tubule. The vas deferens is short and leads to a seminal vesicle containing elongated, vacuolated epithelial cells. No accessory glands were observed tobe associated with the male reproductive system.

Adult Dacus oleae (Gmelin) (Diptera: Tephritidae) reared on 2 different larval diets were extracted with 2:1 chloroform:methanol mixture. Older flies had a greater mean dry and percent dry weight than young flies. Percent total lipids dropped with age on a dry-weight basis. On wet-weight basis this drop was true only for diet N-reared flies. Fractionation on an anion exchange cellulose column showed young females to be richer than older females in the fraction containing the neutral lipids and choline phospholipids. The same was true for young males reared on diet N. Phosphatidyl etlianolamine increased with age in olive-reared females and in diet N reared males and females. The amount of phosphatidyl ethanolamine per total phospholipids varied with sex, fly age, and larval diet. Olive-reared males were richer than females in free fatty acid and phosphatidyl serine fraction, but diet N-reared males were not.

Climate differences across latitude can result in seasonal constraints and selection on life-history characters. Because Aedes albopictus (Skuse) invaded North America in the mid-1980s, it has spread across a range of ≈14° latitude and populations in the north experience complete adult mortality because of cold winter temperatures that are absent in the south. Life-table experiments were conducted to test for differences in the adult survival and reproductive schedules of Ae. albopictus females from three populations from the northern (Salem, NJ; Springfield, IL; Eureka, MO; ≈39° N) and southern (Palm Beach, Palmetto, Tampa, FL; ≈27-28° N) extremes of the species distribution in North America. There were consistent differences between northern and southern populations in incidence of photoperiodically-induced egg diapause. Under short daylength, diapause eggs constituted twice the proportion of total viable eggs from northern females (81.9-92.1%) than southern females (35.9-42.7%). There were no consistent differences between northern and southern populations in resource allocation between reproduction and maintenance, reproduction over time, and reproductive investment among offspring, and no apparent trade-offs between diapause incidence with reproduction or longevity. Our results suggest that the main response of North American Ae. albopictus to unfavorable winter climates is via the life history strategy of producing diapausing eggs, rather than quantitative variation in reproduction, and that there are no detectable costs to adult survival. Inherent geographic variation in the expression of diapause, consistent with the latitudinal extremes of A. albopictus, indicates evolutionary loss of diapause response in southern populations because of the invasion of A. albopictus in North America.

Larvae of the house fly. Musca domestica L., were reared aseptically on a synthetic diet containing cholesterol- 4-C14. Adults obtained from these larvae were fed on a diet containing unlabeled cholesterol to study the utilization and metabolism of the larval sterols for oögenesis. Sterols were initially incorporated into the eggs at 0.53 μg/mg, and rapidly decreased with succeeding oviposition. Hatchability was not significantly affected even when the concentration dropped to 0.15 μg/mg. Esterification of sterols was high in the female flies and increased appreciably in their eggs. Dehydrogenation of cholesterol to 7-dehydrocholesterol was minor in the adult flies, but increased slightly with succeeding collections of eggs.

Pupae of the house fly, Musca domestica L., when exposed to single doses of X-rays, varying between 10,000 to 30,000 rad, show a correlation between dosage and emergence. At 10,000 and 15,000 rad 90.1 % to 73.9% of the flies, respectively, emerge. This figure declines to 42.5% at 20,000 and 19.5% at 30,000 rad. The number of flies dying in the pupal stage correspondingly increases with an increase in radiation dose. The implications of these results are discussed.

A strain of Aedes aegypti (L.), mass selected for resistance to gamma radiation, mated readily with the parent strain and showed no reproductive isolation. Oviposition rates, and usually susceptibility to malarial infection, wore reduced in the selected strain, as well as in the parent stock, which had been irradiated as eggs. After 20 successive generations of inbreeding without exposure to radiation, the offspring of the selected strain continued to show a significantly greater radiation resistance than the parent strain.

An apparatus was constructed to allow simultaneous observation of the thoracic spiracles of adult female mosquitoes and to permit recording of the behavior observed. A microenvironment of controlled composition and relative humidity was provided. In Aedes (Diptera: Culicidae) at rest in air the thoracic spiracles constantly open and close synchronously. The degree of such opening is minimal. Stationary flight, CO2, or hypoxia cause much more extensive synchronized opening. It was suggested that the thoracic compressions and extensions of the head noted in flight or hypoxia are possible ventilatory mechanisms, and were unrelated to the frequency of spiracular opening and closing. Decapitation eliminated spontaneous locomotor activity and resulted in more conservative spiracular behavior.

L(+)-lactic acid in the concentrations given off by human hands was shown in olfactometer tests to be an attractant for avid female Aedes aegypti (L.). The amount recovered by rinsing the hands with acetone ranged from 258 to 1225 micrograms; the amount evaporating from the hands ranged from 23 to 133 micrograms per hour. The regression lines (micrograms lactic acid per percent mosquitoes trapped) obtained in 4 tests with each of 11 subjects were significant, but other factors also influenced individual differences in attractiveness. Vapors from authentic L(+)-lactic acid released from glass sample tubes at rates comparable to those released from hands were attractive either in combination with carbon dioxide (CO2) in filtered air, or alone in room air. However, the synergistic effect of CO2 on the response to lactic acid did not persist more than a few seconds after the mosquitoes left an atmosphere rich in CO3. Breath contained more L(+)-lactic acid than vapor from the hands but was less attractive, probably because it also contained an excess of moisture. D(—)-lactic acid was less attractive than L(+)- lactic acid at low concentrations and in direct competition at higher concentrations. A stocking treated with L(+)-lactic acid at 3.56 milligrams per square centimeter (about 1000–8000 times the amount on hands) was repellent, i.e., the treatment reduced the number of mosquitoes landing and biting. However, in the olfactometer, vapors from this stocking were attractive, at least at a distance of 45 centimeters. Application of a repellent (deet) to the hands did not reduce the amount of lactic acid vapor released.

To determine the effects of drying, flooding, and water temperatures on egg hatch of the yellow-fever mosquito, Aedes aegypti (L.), eggs on roughened aluminum paddles were placed daily for 169 days just above the water level in glass containers in the sun and shade, and daily larval counts were made. By daily measurement of the water level in a standard container, the “hatch indicator,” the combined effects of rainfall and evaporation were determined, and these measurements provided an estimate of the production of A. aegypti from discarded open-topped containers in the field.

The invasive container-dwelling mosquito Aedes albopictus (Skuse) shows modest behavioral responses to water-borne cues from predatory Corethrella appendiculata Grabham in North America. We investigate whether Ae. albopictus adjust their antipredatory responses to be proportional to size-dependent risk of predation. Fourth-instar Ae. albopictus attain a size refuge from C. appendiculata predation, and we compared the responses of second- and fourth-instar Ae. albopictus to cues from C. appendiculata predation. More vulnerable second-instar larvae showed a larger change in behavior in response to predation cues than did less vulnerable fourth-instar larvae, indicating threat-sensitive behavioral responses by Ae. albopictus.

Under alternating light and dark, pupation in Aedes taeniorhynchus (Wiedemann) follows a diurnal rhythm with a period of about 22.2 hr, which may be truly circadian. The period of pupation rhythm is unaffected by temperature but may be lengthened by food deficiency, which prolongs development and may enhance the sharpness of the daily peaks. The emergence rhythm is dependent on the pupation rhythm, separated by an interval affected by temperature but not by photoperiod. Daily pupation episodes come to a peak between noon and midnight at a time set by temperature, diet, and time of hatching. An age threshold at each temperature can prevent the early part of the first pupation episode from expression, resulting in a small “advance peak” late in the day, separated from the next day's peak by less than the 22.2-hr regular period; these advance peaks average 83% males, and can comprise as much as ⅔ of an entire brood's males. The age threshold for pupation, set by the temperature, is nearly the same for both sexes. The 95% limits for a daily pupation increase from 8 hr at 32° to 21 hr at 22°, which indicates a breakdown in the rhythm at the colder temperatures. At full rations, the mean developmental retardation of the female behind the male increases from 5.3 hr at 32° to 14.5 hr at 22°, but only under conditions of food deficiency does it exceed a day. Larval developmental rate is directly related to temperature and amount of food available; it is lower in continuous light than in either continuous dark or alternating 12-hr periods of light and dark. The net effect of the diurnal rhythm of pupation is to reestablish for each experimental hatch group a synchrony of development lost to a remarkable degree in continuous light or dark.

At Madison, Wis., Aedes vexans (Meigen) fed far more actively in prairie and meadow than in a forest, but the reverse was true of A. trivittatus (Coquillett) and some species of the A. stimulans group. Attack rates of A. vexans rose abruptly to a peak at 30–40 min after sunset, then declined gradually. Of 94 collections from man, made by hand in 5–10 minutes at dusk on 94 days, nearly 20% contained more than 100 vexans females (maximum 482), but almost half had less than 30. Sampling of the vexans population by light traps at dusk was not found feasible, because of the high level of feeding activity at that time. In light traps operated from dusk to dawn on 7 consecutive nights, almost 93% of the female vexans taken, and nearly 89% of the males, were captured after 10 PM.

Aedes sticticus (Meigen) is a univoltine species that may have 2 or more broods of larvae each spring. The final conditioning of winterized eggs is a result of rising temperature in the spring. Because eggs occur at all horizons on flood plains and particularly along zones of maximum flood, they may be submerged at different times and after different exposures to spring like temperatures. Embryos remain viable after limited exposure to all post-cold temperatures between 8° and 32°C. Higher temperatures shorten the duration of viability. A temperature of 15°C for both conditioning and hatching caused the highest percentage of hatch over any temperature likely to be experienced in the spring. Prolonged exposures (150 days) to 8°C permitted a moderate survival of embryos.

A laboratory study of the preoviposition behavior of Aedes taeniorhynchus (Wiedemann) is reported. Oviposition in this species was nocturnal in the laboratory and was preceded by a period of flight activity. This activity was exogenously controlled, being initiated by the onset of darkness on the day of oviposition. Flight occurred even in the presence of suitable oviposition substrates, and appeared to enhance the subsequent oviposition response. Females responded to stimuli from oviposition sites during this activity period. The response to moisture was reduced by a high ambient relative humidity, and the sensitivity of the females to a series of repellent salt solutions was reduced when the oviposition response was accelerated by delaying the presentation of substrates. These observations suggest that unnatural conditions imposed in the laboratory may result in acceptance of substrates not normally utilized in nature.

Food, light, and temperature together establish the degree of developmental synchrony in a simultaneously hatched larval population of the black salt-marsh mosquito, Aedes taeniorhynchus (Wiedemann). Periodic starvation does not enhance synchrony, nor does larval crowding per se, nor light regimes divergent from 12 hours light: 12 hours dark, with daylight intensity (>10,000 lux) white light alternating with total darkness. Maximum synchrony is achieved with the highest food ration which will not contaminate the culture and cause extra mortality, at temperatures between 29 and 32°C, with hatching at sunrise of a 12-hour light regime. Approximately 90% of simultaneously hatched larvae can be made to pupate within a span of 12 hours. Such synchronization, never approached in nature with this species, can be very useful in research.

Observations were made on the responses of the thoracic spiracles of adult Aedes aegypti (L.), and adult A. triseriatus (Say) to a constant CO2 pressure in serial concentrations of O2 in N2 and to the O2 in N2 series alone. Less than atmospheric pressures of O2 caused an increase in the frequency and duration of spiracular opening. Higher than atmospheric O2 tensions had no effect on frequency of spiracular opening, but reduced the duration of opening. Carbon dioxide effected full spiracular opening in proportion to the O2 concentration. The duration of spiracular opening, regardless of amplitude, was also proportional to the ratio of CO2 to O2. Responses of Aedes spiracles to hypoxia and CO2 decreased with increasing duration of exposure.

The growth in length of the ventral diverticulum was studied in Aedes triseriatus (Say) and A. aegypti (L.), using standard microtechnical procedures. Growth curves were plotted and they served as bases for comparison. The entire curves for the males of both species were linear at the 1.0% level of significance, while the curves for the females of both species were linear at the same level of significance only in the early hours following pupation. In both species these early hours are characterized by growth of the ventral diverticulum caused by cell division in the anterior imaginal ring, and late growth is due to increase in cell size and a spreading out of the cells. The slope of the curves for both sexes of each species during the period of mitotic growth reflects the rate of mitosis. The linear portions of the growth curves might be useful in studies of the influence of various environmental parameters on the rate of division of embryonic cells during mosquito metamorphosis.

Aedes sticticus (Meigen) is a univoltine mosquito that requires the usual sequence of summer, winter, and spring temperatures for conditioning of eggs. Eggs so conditioned hatch under the stimulus of a decreasing gradient of oxygen. Some eggs hatched at high levels, but most hatched at levels of 10% or below. Levels of 1% and 0% oxyen inhibited hatching in about half of the eggs. Microbial activity in different dilutions of nutrient broth hatched eggs at all temperatures between 8° and 25°C; 15°C provided conditions for maximum hatching with contaminated media. Dilution as great as 1:10000 was most satisfactory at high temperatures and that of 1:1000 was most effective at lower temperatures.