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Since the development of insecticide-resistance and the consequent partial failure of the chemical approach to the control of disease vectors, interest in the biological approach has re-awakened. An aspect of the latter approach that is of great current interest is “autocidal control”—that is, the use of insects for their own destruction. This paper discusses the various ways in which genetic mechanisms can be used to bring about the destruction of harmful insects, with special reference to those of medical importance. The author considers that the prospects for the genetic control of vector species are good, but stresses that before genetic methods can be applied on a field scale certain requirements must be met. For example, genetic technology must be expanded, a firm background of genetic knowledge of vector species must be built up, a great deal more information about vector ecology, particularly population dynamics, must be acquired, and techniques for the mass production of vector insects under controlled conditions must be developed.

Larvae of Aedes hendersoni, Ae. atropalpus, and 6 geographic strains of Ae. triseriatus were compared in terms of their susceptibility to malathion and permethrin. Aedes atropalpus was most tolerant to malathion, whereas Ae. triseriatus (Walton strain) was most tolerant to permethrin. Malathion LC50S for 6 geographic strains of Ae. triseriatus ranked from high to low were: Alabama (ALA)Michigan (UNDERC)Indiana (WAL)Kentucky (UKEN)Texas (SAL)Florida (VB); similar ranking of permethrin LC50S resulted in: WALVBSALUKENUNDERCALA. Differences in susceptibility were detected but were not considered large (i.e., over several orders of magnitude). As a result, no change in application rate of malathion or permethrin, from an operational viewpoint, would be warranted if used against these 3 mosquito species or the geographic strains of Ae. triseriatus investigated.

For many insects, low temperatures are not lethal unless their tissues freeze. To determine whether freezing is the cause of low temperature mortality of Aedes albopictus eggs, we measured their lower lethal temperature, the temperature that causes 50% mortality in a population, and supercooling point, the temperature at which the tissues freeze. Tropical and temperate Ae. albopictus eggs were tested under different diapause and cold acclimation conditions. Temperate Ae. albopictus eggs had a lower lethal temperature than tropical Ae. albopictus eggs. Diapause and cold acclimation decreased the lower lethal temperatures of temperate eggs. However, neither diapause, cold acclimation, nor geographic origin affected Ae. albopictus egg supercooling points. All lower lethal temperatures were above -13 degrees C and all supercooling points were below -26 degrees C, indicating prefreeze mortality. Eggs of Aedes triseriatus and Aedes aegypti also died before they froze.

Field-reared Aedes albopictus were marked with fluorescent pigment upon release and recaptured with a vacuum aspirator at a scrap tire yard and in surrounding vegetation in Potosi, MO, during 1989-90. In 8 dispersal trials, 8.1% (1,100/13,513) of the Ae. albopictus were recaptured with 84.4% (928/1,100) collected in the forest edge ecotone between 10 and 600 m from the release point. The maximum dispersal distance recorded was 525 m and 11.1% (122/1,100) dispersed further than 100 m. In 3 survival trials, 4.8% (2,660/55,284) of the mosquitoes were recaptured. Adult Ae. albopictus females survived an average of 8.2 days (probability of daily survival [PDS] = 0.89, range = 0-24) and males an average of 3.9 days (PDS = 0.77, range = 0-12). The dispersal and survival capacity of Ae. albopictus adults may contribute to the spread and potential health threat of this mosquito in the USA.

Bloodfed Aedes albopictus were collected during 1989-91 by vacuum aspirator from rural and urban study sites in Missouri, Florida, Indiana, Illinois, and Louisiana. Blood hosts identified by ELISA and precipitin tests were rabbit (n = 91), Rattus sp. (n = 69), dog (n = 14), unidentified mammal (n = 14), cow (n = 13), human (n = 10), deer (n = 10), sciurid (n = 7), turtle (n = 5), murid other than Rattus sp. (n = 4), raccoon (n = 3), passeriform bird (n = 3), and cat (n = 2). As an opportunistic bloodfeeder, Ae. albopictus may be a potential vector of domestic arboviruses and a nuisance pest where infestations occur.

Aedes albopictus (Skuse) lays eggs refractory to hatching in response to several environmental cues. The goal of this statistical treatment was to quantify the role and interaction of latitude and country of origin (Japan and the United States), photoperiod, rearing/holding temperature, and a newly identified element, elevation of the site of origin, with critical photoperiod (Cpp). We also describe the development of an equation relating the incidence of diapause to daylength, rearing/holding temperature, and latitude and elevation of the site of origin, an equation useful in the development of a simulation model of the population dynamics and distribution of Ae. albopictus in North America. The analysis indicated that elevation from 0 to 300 m is significantly correlated with Cpp. The results also corroborate earlier conclusions that, on the basis of a shallower geographical cline in photoperiodic response in the United States, North American strains of Ae. albopictus have a temperate origin in Asia and indicate that the rapid spread of this mosquito within the United States via the distribution of used tires resulted in founder populations that were only partially adapted in diapause response to local conditions.

Mermithid parasites (Nematoda: Mermithidae) were observed in 11 mosquito species in 22 counties of Indiana, Michigan, Minnesota, Ohio and Wisconsin. Natural hosts included adult Aedes vexans, Ae. canadensis, Ae. cinereus, Ae. diantaeus, Ae. punctor, Anopheles punctipennis and Coquillettidia perturbans and larvae of Ae. abserratus, Ae. canadensis, Ae. cinereus, Ae. communis, Ae. diantaeus, Ae. provocans, Ae. punctor, Ae. stimulans and Cq. perturbans. These are the first records of such parasites in Indiana, Minnesota, Ohio and Wisconsin.

Eggs of temperate Aedes albopictus populations are cold hardy and can diapause, but tropical populations are not cold hardy and cannot diapause. Heterozygotes possess intermediate diapause and cold hardiness. Males of a tropical strain from Malaysia with a distinctive genetic marker were released into an existing temperate population in East St. Louis, Illinois. Subsequent egg samples from the release site had genetic marker frequency of up to 24%. Reduced cold hardiness and decreased diapause incidence were also observed in the release site population. No such changes occurred at a nearby control site. The rank order of overwintering survival of eggs at the release site was: Aedes triseriatustemperate Ae. albopictushybrid temperate/tropical Ae. albopictustropical Ae. albopictus. Eggs collected from the release population the next summer showed total absence of the genetic marker; presumably carriers were removed by the winter.

Precipitin tests and ELISA were used to investigate host-feeding patterns of 172 blood-fed Aedes albopictus (Skuse) collected at Potosi, MO, during the summers of 1989 and 1990. One hundred ten (64.0%) mosquitoes had fed on mammals, 29 (16.9%) on birds, and none on turtles or snakes. Thirty-three (19.2%) mosquitoes failed to react in all tests. Eighty-six (78.2%) of the 110 mammalian feeds were positive for lower taxa as follows: rabbit, 24.5%; deer, 14.5%; dog, 13.6%; human, 8.2%; squirrel, 7.3%; opossum, 4.5%; myomorph rodents other than Rattus, 3.6%; raccoon, 0.9%; and bovine, 0.9%. Positive feeds were not detected for the following mammals: cat (n = 99); horse (n = 95); Rattus (n = 84); and swine (n = 84). Fourteen (48.3%) of the 29 avian feeds were positive for lower taxa as follows: Passeriformes, 24.1%; Columbiformes, 17.2%; Ciconiiformes, 3.4%; and quail, 3.4%. These data, the first on host-feeding patterns for Ae. albopictus populations in the New World, indicate that Ae. albopictus is an opportunistic feeder that utilizes a wide variety of hosts and, therefore, has the potential to become involved in the transmission cycles of indigenous arboviruses.

Photoperiod induced dormancy for 14 North American strains of Aedes albopictus were determined at 21, 26 and 29 degrees C. Strains tested at 21 degrees C and intermediate temperatures of 25-27 degrees C demonstrated clear photoperiodic responses whereas temperatures of 29 degrees C and above, greatly reduced or negated diapause incidence. A suboptimal larval diet increased the percentage diapause in eggs laid by resulting adults. This larval diet was also associated with a slight increase in critical photoperiod.

Blood samples of 34 Eastern chipmunks trapped in the vicinity of an Aedes albopictus population near New Alsace, IN, were tested for neutralizing antibodies to La Crosse (LAC) virus and other California group viruses. Two samples were positive for LAC antibodies. Analysis of mosquito bloodmeals demonstrated that both Ae. albopictus and Ae. triseriatus from the site fed on chipmunks. This note documents the first record of LAC antibodies in sylvan rodents from Indiana, the presence of LAC virus in the vicinity of Ae. albopictus and that wild Ae. albopictus feed on Eastern chipmunks.

Juvenile hormone, the secretion of the corpus allatum, apparently controls the secretory process of the male accessory glands of the yellow fever mosquito, Aedes aegypti. Topical application of a juvenile hormone mimic induces precocious and enhanced secretion. The treatment with the JH mimic not only increases the potency of males to inseminate more numbers of females, but also stimulates secretion in fully depleted glands of A. aegypti which under normal conditions do not renew the secretory process. Males whose accessory glands are depleted due to multiple matings and later treated with the mimic also inseminate. Cauterization of the corpus allatum complex has prevented the secretory function in the glands.

Palp-antenna is a homeotic mutant of Aedes aegypti that modifies the apex of the maxillary palps of both sexes into a variable number of antenna-like segments. The fine structure of the antenna, including sexual dimorphism, is apparent in the mutant palps. Palp-antenna is a sex-linked recessive. a linkage distance of 27.9 +/- 0.45 crossover units from sex is estimated from F2 and backcross data. Penetrance is complete; expressively is variable. The fitness of the mutant compares favorably with that of the wild type. The mapping of the ppa locus lengthens the known chromosome 1 linkage map of Aedes aegypti.

In Aedes aegypti, the ’matrone’ substance which caused mating inhibition and stimulated oviposition in females, was present in the anterior secretory region of the male accessory glands. In the divided accessory glands of male A. triseriatus, however, it was present in the posterior glands. The posterior gland substance in A. triseriatus was not species specific. It stimulated oviposition in A. aegypti and caused mating inhibition in A. atropalpus. The secretory substance of the posteriormost region in the glands of both species of mosquitoes was mucin in nature. This mucin substance effectively glued the secretory granules of the anterior region(s).

Striations are one type of substructure which can form in metals as they solidify from the melt. The formation of striations is dependent upon the rate of crystal growth, the purity, and the crystallographic orientation. In aluminum single crystals, it was found that striation boundaries tended to approach a preferred (100) growth direction with increasing rate of growth and with increasing solute concentration. With different types of solute, it appears that similar values of the average concentration of solute in the liquid at the solid–liquid interface (C0/k) produced the same effect on striation direction.The number of striations found in any sample appeared to be a complex function of the purity, the orientation, and the rate of growth.

The tensile plastic deformation of single-crystal and tricrystal specimens of zinc was investigated by analysis of the external change in shape of the specimens, and of the changes in X-ray diffraction patterns. It was demonstrated that the single crystals deformed by slip on the basal plane, but pyramidal as well as basal slip occurred in specimens containing grain boundaries.

The literature reports values ranging from 8000 to 26,000 cal per g-atom for the activation energy for the creep of tin. The present investigation analyzed the results of constant stress creep tests during steady state creep, and by means of temperature cycling. A value of approximately 9000 cal per g-atom for the creep of high purity tin in the temperature range 300 to 350° K was obtained.

Large single crystal segments of aluminum were produced by strain anneal, deformed in tension, and sectioned to produce tensile specimens with axes parallel to the original tensile axis and with other orientations. The specimens were annealed to produce a polygonized substructure. Their critical shear stress in tension was determined. The critical shear stress was shown to be the sum of a substructure independent stress and a stress proportional to the square root of the average primary subboundary misorientation over the average primary subboundary spacing. Comparison of the critical shear stress of specimens cut from the same parent crystal with varying tensile axes demonstrated that the significant subboundary spacing is that between primary subboundaries along the active slip plane of the specimen. The tests also showed that average subboundary misorientation is significant because it represents the average spacing of dislocations in the subboundaries. The results, interpreted in terms of current substructure strengthening theories, indicate that slip is propagated across primary subboundaries by the activation of dislocation sources in the subboundaries.

Polycrystalline copper specimens have been tested in variable stress creep and in constant stress creep at room temperature. In variable stress creep tests, the ratio between the stress change Δσ and the creep strain was held constant so that Δσ ϵ = −λ where λ is a spring constant. In these tests, the dependence of stress change on time t could be represented by a logarithmic relation Δσ ≅ S ln (ct + 1) which agrees with the prediction of Mott's theory of creep. A theoretical analysis indicated that for polycrystalline copper the factor S could be related to the activation volume V by an equation of the form S = − σ 0 τ 0 kT V where τ0 is the average shear stress resolved in the shear direction and V the activation volume. The relation between S, the applied stress σ0 and the spring constant λ was investigated in the range of 4.8 ⩽ σ 0 ⩽ 29.4 kg/mm 2 0.62 ⩽ gl ⩽ 5 × 10 3 kg/mm 2 . It was found that S was a function of both the applied stress and the spring constant. At constant gl the factor S increased linearly with increase in stress. At constant stress level the factor S increased with increase in λ but not linearly.

We conducted experiments to assess the importance of winter cold and photoperiod as factors affecting the spatial and age distributions of overwintering larvae of the treehole mosquito Anopheles barberi. Larval dormancy in A. barberi was induced by photoperiods with 14.75 h of light or less per 24 h cycle. About 75% of the larvae entering dormancy were in the second instar regardless of photoperiod. Dormant second instar larvae survived freezing at-15° C for 24 h better than dormant third instar larvae. Larvae were more likely to survive freezing at-15° C in water from treeholes in which they were commonly found in nature than in water from treeholes in which they were unlikely to occur. Female oviposition was significantly higher into water from treeholes in which larvae were likely to be found than in either water from treeholes in which larvae were not commonly found or distilled water. These findings suggest that, in the northern part of its range, the distribution of A. barberi and the age structure of overwintering cohorts are influenced by extreme winter cold. The mechanisms responsible for the distribution of larvae and the overwintering age structure are, respectively, female oviposition behavior and larval photoperiodism.

A population of Aedes albopictus collected in 1986 in Harris County, Texas, was evaluated for its vector competence with 4 California serogroup viruses (Jamestown Canyon, Keystone, La Crosse and trivittatus). Rates of midgut infection, dissemination of virus beyond the midgut and oral transmission to suckling mice were markedly different for the 4 viruses in a pattern representative of the antigenic relationships known for the California serogroup. Only La Crosse virus was shown to be efficiently transmitted by this recently introduced mosquito population. The results suggest that populations of Ae. albopictus originating from the Harris County population might well be as efficient in transmitting La Crosse virus as are populations of the natural mosquito vector. Aedes triseriatus, from the midwestern La Crosse virus enzootic region. The public health implications of these results are discussed in relation to the rapid spread of Ae. albopictus throughout the eastern half of the United States and into regions where La Crosse virus is known to be enzootic.

Ovitraps were used to determine the distribution of Aedes triseriatus among forty-eight 1.2 km2 quadrants in urban South Bend and Mishawaka, Indiana. Oviposition paddles from 96 ovitraps were collected for 13 weeks from June to September, 1986. A total of 82,974 eggs was collected. Eggs were present in each quadrant at least once and were found in most quadrants on 6 or more collection dates. Ninety-two percent of the ovitraps were positive at least once, indicating ubiquitous distribution throughout the urban area. The eggs collected were 80-90% Ae. triseriatus, the remainder being Ae. Hendersoni. Effectiveness of large (3,100 ml) and small (350 ml) ovitraps was compared. The large ovitraps exceeded the small by 319% for eggs/positive ovitrap and 486% in numbers of positive ovitraps.

An arbovirus survey was conducted during August 1985 at White Sands Missile Range in southcentral New Mexico following a suspected arboviral disease epizootic among feral horses. A total of 20,566 mosquitoes (18,505 females and 2,061 males) and 8,900 biting gnats were collected and assayed for virus. Female mosquitoes were principally Aedes campestris (54.8%), Aedes dorsalis (30.4%) and Culex tarsalis (13.2%). Arboviruses were not isolated from biting gnats, but mosquitoes yielded a total of 37 viral isolates, including western equine encephalitis (WEE) (18), California serogroup (15), Cache Valey (1), and Hart Park (1) viruses in addition to 2, as yet unidentified, rhabdoviruses. Isolates of WEE virus were from 9 pools of Ae. campestris, 6 of Cx. tarsalis and 3 of Ae. dorsalis. California serogroup viruses, including 2 subtypes, were obtained from 7 pools of females and 1 pool of males of Ae. campestris and from 4 pools of Ae. dorsalis. Cache Valley and Hart Park viruses were isolated from single pools of Ae. dorsalis and Cx. tarsalis, respectively, and the rhabdoviruses were obtained from Ae. campestris and Psorophora signipennis.

In the past, Aedes atropalpus was limited to those areas of the eastern U.S. and Canada that had rivers or shorelines with large rocks containing rock pools. In the last 10 years, many new records of larval breeding in scrap tires have accumulated. We present records of larval breeding in non-rock pool containers for 54 counties; most are far from the original range. The species has not only found a new habitat but has greatly extended its range via commercial transport of scrap tires.

We analyzed the progeny of brother-sister matings of two inbred strains of the treehole mosquito, Aedes triseriatus, at several isozyme loci to determine which factors were maintaining heterozygosity at these loci after prolonged inbreeding. The triseriatus Kramer (TK) lines were polymorphic for the Odh and Hbd loci after 12 generations of full-sib mating, and the triseriatus Vero Beach (TV) lines were polymorphic for the Odh, Hk-4, Pgm, and Hbd loci after 14 generations of full-sib mating. Genetic analysis of 22 TK F13 matings and nine TV F15 matings showed that heterozygosity was enforced by lethal loci to which all the polymorphic isozyme loci were linked. The lethal loci formed a balanced lethal system. We determined the relative positions and map distances of lethals and enzyme loci.