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The host blood sources of 5 species of Culex collected from several sites on both Florida coasts were identified by precipitin tests. Results indicate that in Florida (1) Culex territans is essentially a parasite of cold-blooded vertebrates as it is elsewhere, (2) Culex Pipiens quinquefasciatus is a general feeder, mostly on domestic birds and mammals, and passerines, (3) Culex salinarius is also a general feeder but C. salinarius tends to feed primarily on mammals in certain habitats, (4) Culex nigripalpus is an extremely opportunistic mosquito which feeds mainly on cattle and rabbits, and ciconiiform, passerine, and galliform birds. C. nigripalpus showed an annual shift in feeding during all 6 years of the study. This vector species feeds mainly on avian hosts in winter and spring and then shifts to near equal or greater feeding on mammals in summer and fall. The time and magnitude of the shift varied from year to year in correspondence with the onset and duration of the rainy season. Possible explanations for the feeding shift are discussed and evidence in support of a seasonal change in mosquito flight habits as a result of changing moisture levels is presented.

The threshold of infection with Wesselsbron virus was lower for Aedes aegypti than for Culex quinquefasciatus , but after ingesting higher doses of virus, C. quinquefasciatus more frequently became infected. Nevertheless, once infection was initiated in A. aegypti , the virus replicated to a high titer in a greater proportion of mosquitoes. The net result was that A. aegypti , after ingesting small amounts of virus, transmitted virus more efficiently and after a shorter extrinsic incubation period than C. quinquefasciatus ; after the ingestion of high doses, both species transmitted infection with equal efficiency.

The effect of infection of larvae of the mosquito Culex pipiens quinquefasciatus by the fungus Lagenidium giganteum has been studied from a biochemical standpoint. Methods were developed to analyze larval extracts that were essentially free of parasitic material. Biochemical parameters investigated on a per larva basis were protein, and the enzymes o -diphenol oxidase, glutamate transaminase, alkaline phosphatase, trehalase, and chitobiase. The behavior of the total amino acid and sugar pools were also examined. In general it was found that the infected larvae exhibited a significant decrease in rate of synthesis of most of the parameters studied and that the rates eventually fell to zero when compared to healthy control organisms. The progress of mycosis was correlated with visual evidence and it was concluded that the larvae were dying from starvation as a consequence of the utilization of their endogenous reserves by the parasite. Death of the larvae occurred as a general rule, in laboratory conditions, some 48 hr after initiation of infection by the fungus.

While the authors were engaged in studies on mosquitoes'in relation to epidemiology of Japanese encephalitis in Okayama Prefecture, western Honshu, a large number of mosquito species belonging to the subgenus Barraudius, genus Culex were collected. By comparative studies with the known species of the subgenus, the present species has been recognized most closely related to Culex B however, it differs in several morphological characters from those de- scribed by previous authors for the nominate form, especially in the structure of appendages on the subapical lobe of male genitalia. A new subspecies, Culex &Bar. raudius& modestus inatomii, is created, and its male, female, pupa and larva are described in this paper. The females of the present subspecies are voracious human biters. The immature stages were found in brackish water.

The reproduction of mosquitoes, and to a lesser extent other biting flies, is briefly reviewed. Special attention is given to spermatogenesis, follicular development, and fertilization.

The planarian, Dugesia dorotocephala (Woodworth), was studied in the laboratory and field as a predator of all developmental stages of Culex peus Speiser. Reproduction by transverse fission was accelerated by higher feeding rates and probably by crowding. Decreased feeding in culture could be offset by increasing the density of Dugesia . Experimental field populations of Culex larvae were reduced by 90+% in 26 days during July and August, 1973. Mucus secretions effectively immobilized prey larvae and their body fluid was consumed. Mucus was also used to produce cemented sand anchors for attachment to larvae and pupae. Group feeding without internecine activity was observed whereby as many as 12 Dugesia collectively ensnarled a single prey. Field and laboratory observations indicated optimum temperatures for feeding and reproduction were 20–26°C. Feeding ceased above 29°C; mortality ensued at 30°C.

SummaryThe findings of a survey on the ecology of an alphavirus over the years 1964–9 are reviewed. Evidence is presented to show that wild birds constitute a vertebrate reservoir of the virus and that mosquitoes, primarily Culiseta tonnoiri and Culex pervigilans, which are both endemic New Zealand species, are responsible for summer transmission.Serological evidence of infection was obtained in all years and evidence is presented to indicate that the virus is enzootic rather than being reintroduced each spring. The number of birds with antibody increased before mosquitoes became active in the spring and possible explanations of this are discussed.The mean temperature in the hottest month in the study area is substantially below that in other areas with enzootic mosquito-borne viruses and experimental studies showed that Whataroa virus was able to replicate more rapidly in mosquitoes at low temperatures than any arboviruses previously studied.The main natural focus of infection appeared to be in a modified habitat and the introduced song thrush (Turdus philomelos) to be the main vertebrate reservoir host.

Para-aminobenzoic acid (PABA) administered in the diet in 0.01, 0.1, 0.2, 0.3, 0.4, and 1.0% concentrations to Aedes aegypti was found to enhance oocyst production. The most significant increase in oocyst production was in groups receiving 0.3 and 0.1% solutions. A combination of 0.01% PABA + 0.1 M NaOH, and 0.02 M HCL, 0.1 M KOH, 0.1 M NaOH, and 0.2 M MgCl2 likewise increased the susceptibility of A. aegypti to Plasmodium gallinaceum with 0.1 M NaOH being the most effective. Culex pipiens pipiens was found to exhibit a low degree of susceptibility to P. gallinaceum. This is the first report of oocyst development by P. gallinaceum in this species. PABA in 0.1, 0.2, 0.3, 0.4, and 1.0% concentrations was tested and all concentrations increased the susceptibility of this refractory host. This compound was most effective in a 0.4% concentration. The susceptibility of C. pipiens pipiens to P. gallinaceum was also increased by inorganic materials. NaOH and KOH in 0.1 M concentrations yielded the greatest increase. A slight increase in susceptibility was effected by 0.2 M MgCl2 and 0.02 M HCL. Culex receiving the combination of 0.01% PABA and 0.01 M NaOH had the highest infection of those receiving inorganic compounds. Most of the oocysts produced in these experimental Culex were fairly typical of those found in A. aegypti; however, some were quite small and others showed evidence of deterioration, distortion, and shrinkage.

Eight sex-linked translocations and two pericentric inversions were artificially induced and isolated in the mosquito Culex pipiens fatigans. Following extensive studies on the genetics and cytology of these aberrations, correlations between the three pairs of chromosomes and the three linkage groups were established. Chromosomes 1 (shortest), 2 (longest) and 3 (intermediate) are correlated to linkage groups I, II and III respectively. These conclusions are in conflict with an earlier publication. A secondary constriction was observed on the m (but not on the M) chromosome near the centromere. Its significance is not yet clear. The genetic and cytological data indicate that the gene y may be located on the long arm and the gene ru on the short arm of chromosome 2.

Mosquitoes from laboratory colonies were allowed to feed on chicks circulating virus at various levels or, in 1 experiment, on 2 blood-virus suspensions. Subsequently the transmission of virus by individual mosquitoes to individual chicks was tested, the mosquitoes having been held at 26°C or, in 1 case, 18°C. With mosquitoes infected on an optimal viral dose and held at 26°C, 100% transmission rates were obtained on the 7–8th, 41st and 49th day after the infective feed and mosquito infectivity was still 100% after 81 days. A reduction in temperature for the post-infection period from 26 to 18°C caused a drop in the transmission rate from 97 to 48%. This indicates the influence weather conditions would be expected to have on transmission by wild populations of C. univittatus . A reduction in the infecting titer from 5.0 to 2.6 logs in mosquitoes held at 26°C caused a decrease in transmission rate from 89–33%. This underlines the importance of the level of infecting dose chosen for transmission tests.

(1974). Arbovirus infections in Sarawak, October 1968—February 1970: Japanese encephalitis virus isolations from mosquitoes. Annals of Tropical Medicine & Parasitology: Vol. 68, No. 4, pp. 393-404.

An evaluation of the susceptibility of eight mosquito species to Sindbis virus was conducted as a prelude to studies on the mechanisms of arbovirus infection in mosquitoes at the cellular and molecular level. Culex tritaeniorhynchus was the most susceptible mosquito tested, with an ID10 of 2.42 log10 TCID50. Considerably higher infectivity thresholds were observed with C. salinarius (4.41) and Aedes aegypti (4.46), but these species did show persistence of virus which may indicate multiplication. Anopheles quadrimaculatus, An. stephensi, Aedes taeniorhynchus and Ae. triseriatus became infected only at high doses and all showed reduced virus titers after 7 days post-infection. Armigeres subalbatus were refractory to infection at all doses tested.

The isolation in Kenya of arboviruses from mosquitoes and patients is reported. Middelburg and Semliki Forest virus (group A), Banzi virus (group B), Bunyamwera and Beliefe virus (Bunyamwera group), Sango virus (Simbu group), Pongola virus (Bwamba group), Tahyna virus (California group), ungrouped AR 1169/64 and a number of viruses still to be identified were isolated from mosquitoes. Of the latter some may be hitherto undescribed viruses. Bunyamwera, Rift Valley Fever and 2 unidentified viruses were isolated from patients. The isolates are discussed against the background of information from isolations and serology performed elsewhere. Attempts are made to define their role in human disease. Some superficial suggestions about the ecology are made.

Light-trap collections of mosquitoes were made at 2 pig-raising areas and at 1 semi-urban control collecting station near Jakarta, Indonesia from December 1971 through January 1973. Culex tritaeniorhynchus was the predominant species collected from rural stations. In pig areas, mosquito densities were highest during the rainy season, but a distinct increase in numbers was also recorded during the middle of the dry season, in July and August 1972. The dry season increase could not be explained by influence of rice culture practices on mosquito breeding, since it was most marked at the control, semi-urban collection site.

Plasmodium vaughani Novy and MacNeal, 1904 , Plasmodium tenue Laveran and Marullaz, 1914 , and Plasmodium merulae Corradetti and Scanga, 1972 are shown to differ. It is suggested that P. tenue and P. merulae should be considered as subspecies belonging to Plasmodium vaughani -complex. More investigations are needed for a sufficient knowledge of the complex, particularly because at least 36 species of birds harbor P. vaughani -like parasites and cover an immense geographical area in all the parts of the world.

An experimental study of the mechanisms and patterns of resistance to Plasmodium berghei in different mosquito species revealed a diversity of factors which prevent or inhibit sporogonic development in its different phases and in different sites in the mosquito vector. The experiments showed that Culex salinarius was a totally resistant species in which exflagellation and ookinete formation are prevented. In Aedes aegypti, ookinetes in small or moderate numbers are formed but penetration of the mosquito midgut wall is blocked and oocysts are not formed. In the three experimental vectors, Anopheles quadrimaculatus, Anopheles aztecus, and Anopheles stephensi grades of enhanced susceptibility are recognized. They are expressed in lesser numbers of abnormal and degenerative oocysts, in higher numbers of sporozoites in the salivary gland, and greater viability and invasiveness of these sporozoites. In Anopheles dureni, the natural vector of rodent malaria, one observes both in nature and under experimental conditions the highest adaptation and most pronounced grade of susceptibility to P. berghei.

The long range orientation of West African mosquitoes to birds was studied using ramp-traps set up 3–23 m from the bait. The baits comprised chickens, ducks, pigeons and the carbon dioxide equivalent of the chickens. From the pattern of convergence of mosquitoes to the baits, it was shown that Anopheles melas Theo. and Culex thalassius Theo. were orienting to all the bird-baits from distances of at least seven metres. Responses to carbon dioxide were only apparent at a distance of three metres indicating the greater range of effect of the chickens over their carbon dioxide equivalent. Mosquitoes of the largely bird-biting C. decens group showed no long range response to any bait, even though they were entering pigeon-baited traps and to a limited extent feeding on the birds. Catches of A. melas in bird-baited traps were larger at the foot of a tall tree than in the foliage at 5·33 m; for Culex spp. the converse was true. Catches of Culex at 5·33 m outside the tree were smaller than within the foliage.

Venezuelan encephalitis virus, an RNA-containing virus, uniformly grew to high titers in Aedes aegypti and A. triseriatus mosquitoes following intrathoracic inoculation. The minimal intrathoracic infectious dose per A. triseriatus was about 10 chicken embryonic cell culture pfu whereas the minimal oral dose was about 10,000 pfu. In contrast, only some inoculated C. tarsalis and very few C. pipiens quinquefasciatus supported viral growth. Failure of VE virus to grow in C. tarsalis and C. p. quinquefasciatus was probably not caused by virus inhibitors in mosquito tissues since no virus inhibitors were found in triturated mosquitoes of the 2 Culex or 2 Aedes species. Three RNA-containing non-arboviruses, Coxsackie A5 and A7 and Rous sarcoma, and 2 containing DNA, herpes simplex and vaccinia, did not multiply in Aedes aegypti following intrathoracic inoculation, nor did Rous sarcoma virus grow in Culex p. quinquefasciatus . Persistence of infectious Coxsackie A7 and vaccinia viruses for at least a week in mosquitoes indicated that isolations of these and similar viruses from mosquitoes collected in nature might represent virus survival without multiplication.

Summary and Conclusions From January, 1956, through April, 1960, 171,210 culicine mosquitoes from Ndumu, Natal, Union of South Africa, were inoculated into mice in 2,325 lots for attempted virus isolation. Fifty-nine recoveries of viruses were effected. The viral isolates, including nine identified viral types, were recovered from nine species of mosquito, but among these the only ones principally concerned were Aedes (Neomelaniconion) circumluteolus (Theobald), Culex (Culex) univittatus Theobald, Mansonia (Mansonioides) africana (Theobald) and Mansonia (Mansonioides) uniformis (Theobald), in the order named. The incidence of viral isolates in time and space at Ndumu indicates the possibility of the following assumptions having some basis in fact: (a) host specificity of most of the viruses concerned is not strict among genera of the tribe Culicini; (b) the virus types occurring in the Ndumu region may have undetected local cryptic cycles, their episodic reappearances being accounted for less by foreign reintroduction than by the occasional conjunction of ecological conditions that permits them to enter mosquito cycles detectable by current methods of investigation.

Delta, a new mutant of the mosquito Culex tritaeniorhynchus is described. Genetic analysis revealed that this gene is dominant and closely linked to sex. The possibility of using this gene to detect cryptic variabiltiy in the sex chromosomes of natural populations of this mosquito is discussed.

Vector mosquito populations, arbovirus infection rates among mosquitoes and avian hosts, sentinel chicken flock transmission indices, and human clinical and inapparent arbovirus infection rates were monitored to evaluate the effectiveness of ultra-low volume (ULV) applications of malathion for control of arthropod-borne encephalitis in Hale County, Texas, during 1967. Effective control of arbovirus activity was not obtained by weekly treatments of towns with areas of approximately 17 and 65 km2 (6.5 and 25 square miles). Barrier treatments between the towns and the areas of Culex tarsalis breeding may have reduced infiltration of infected vector mosquitoes into the treated towns. Retreatment at 3-day intervals also may have resulted in sustained vector control and reduced arbovirus activity.

1. 1. Culex tarsalis females selected water containing pupae, exuviae and emerging adults of their own species for oviposition in preference to distilled water. 2. 2. Preference was shown for water which had contained these stages (emergence water) even after they had been removed by filtration. When this water was boiled and offered to C. tarsalis females with an unboiled sample of the same water, preference was shown for the boiled material. 3. 3. Evaporation of a volume of emergence water was followed by reconstitution of the dry material with distilled water or with 0·03M NaCl solution. The reconstituted samples were selected by ovipositing C. tarsalis females when offered together with distilled water or 0·03M NaCl. 4. 4. Ovipositing C. tarsalis females selected emergence water which had contained the same species in preference to emergence water obtained from Culiseta inornata, Aedes aegypti and Culex pipiens . 5. 5. Emergence waters which contained C. tarsalis males and females respectively were equally acceptable to C. tarsalis females. 6. 6. No discrimination was made by ovipositing females between water which had contained C. tarsalis 4th-instar larvae and emergence water of the species. 7. 7. No clear discrimination was made by ovipositing females between emergence water and water which had contained only pupae of the species. 8. 8. A similar type of behaviour was demonstrated by Culex pipiens but not by Aedes aegypti females.

Portable, intermittent, battery-operated host-preference traps which held small vertebrates were used to collect 2614 mosquitoes attracted to birds, mammals, reptiles, and amphibians during the summer of 1963. Many Culiseta melanura (Coquillett) and Culex p. pipiens L. females engorged on reptiles and amphibians, although they were primarily ornithophilic. Aedes canadensis (Theobald), C. restuans Theobald and Mansonia perturbans Walker engorged on all 4 classes of vertebrates, but the 2 last-mentioned species preferred birds, mammals, or amphibians to reptiles. C. territans Walker fed only on coldblooded animals. Nine new host-feeding records were obtained for Culiseta melanura, 10 for Culex pipiens, 14 for C. restuans, 4 for C. territans, 7 for M. perturbans, 7 for A. canadensis, 4 for A. aurifer (Coquillett), 4 for A. abserratus (Felt & Young), 4 for A. cinereus Meigen and 4 for A. excrucians (Walker).

Few, if any, groups of mosquitoes present greater taxonomic confusion and difficulty than does the subgenus Melanoconion . At the present time, the species can be recognized with certainty only by the structures of the male terminalia. The females of most species can not be separated from one another; they are usually small and dark-colored, only a few having a distinctive golden-scaled scutum or white-ringed tarsi. The larvae of many species are readily recognizable, but for the most part they are insufficiently known to permit positive identification.

Several aspects of the biology of Amoebidium parasiticum were studied with Aedes aegypti as a major host. In the life cycle of the fungus, presence of two reproductive phases, sporangiospore phase and amoeboid-cyst phase, were confirmed. However, fusion of amoeboids, which was reported earlier, was not observed. Variations in vegetative growth of the thalli and fungal association with other microorganisms in natural conditions were observed. The fungus grew well on all parts of the external surface of the insect, but a particular preference was noted for antennae and anal gills. The fungus has a broad host spectrum, attaching on the species of Cladocera, Copepoda, Culex , and Aedes . However, growth was poor on Anopheles . The fungus never attached on the local species of Ostracoda. The fungus does not cause mortality among Aedes aegypti larvae under optimal rearing conditions for the host, but under starvation mortality of fungus-associated larvae increased significantly over that of controls. A heat-stable, dialyzable fraction of the homogenate of Aedes aegypti increased the percentage of amoebogenesis. Three hormones, eedysterone, juvenile hormone, and diosgenin, were also tested for their amoebogenicity, but the results were negative.

Eggs of Culex pipiensL. are laid in rafts on the surface of still or slow moving water, whereas those of Mansonia africana (Theobold) are deposited beneath tho surface of the water on the undersides of floating leaves (Laurence & Smith 1958; Laurence 1959). The eggs of both species are surrounded by air, those of Culex pipiens are in direct contact with the external atmosphere, whereas those of Mansonia africana are partially surrounded by a bubble of air trapped between them. The anterior onds of the eggs of Mansonia africana project through the bubble of air into the surrounding water. This bubble of air is only found around living eggs and disappears if tho eggs die and shortly before they hatch. Iyengar (1935) has shown that the eggs of Ficalba minima Theo. although often deposited on the same leaf as those of Mansonioides, are laid above the water line and resemble in structure those of Culex and Coquillettidia. The structure of the egg-shell of both Culez pipiens and Mansonia africana is described and discussed.

Vector populations were measured and virus isolations were made in order to follow the annual cycle of infection. The cycle was correlated with the appearance of infection in pigs. Laboratory transmission tests with pigs and mosquitoes measured the level and duration of viremia in relation to pig age and antibody level, and related these factors to the proportion of mosquitoes infected.

Culex stigmatosoma was described by Dyar (1907) from a large number of specimens that had been collected mostly from California. A rather general description was given for the larva, but Dyar stated that the larva would fall into the table of Dyar and Knab (1906) with pipiens and cubensis.

The blood meal source for 4,957 engorged mosquitoes collected from 1964 through 1968 was determined by a capillary precipitin technique. Culex tarsalis and Aedes vexans comprised most of the specimens tested; other species tested included Aedes nigromaculis, Anopheles punctipennis, Culex quinquefasciatus, Culiseta inornata, and Psorophora signipennis. The predominant feeding of Aedes, Anopheles, Culiseta, and Psorophora was upon mammals, and of Culex quinquefasciatus upon birds. The C. tarsalis feeding pattern varied widely, and the proportion that had fed upon birds ranged from 42% in 1966 to 83% in 1965. An analysis of forage ratios provided an index of host preference of C. tarsalis in 1966. The data reported further substantiate the role of C. tarsalis as the principal vector of western equine encephalitis and St. Louis encephalities in the western United States.

Summary During the 22 months of a collaborative study carried out in Almirante, Panama, 1,341 pools comprising 181,979 mosquitoes and Phlebotomus sandflies were inoculated into suckling mice and hamster kidney cell cultures. Thirty-nine viruses were thus isolated which were classified as 9 types of 5 recognized groups, and one previously undescribed, totally distinct agent. Previously unknown on the Isthmus of Panama were: Una virus of group A, Guaroa, Cache Valley and Wyeomyia-complex viruses of the Bunyamwera group, and a member of the Guama group. The most noteworthy finding was the repeated isolation from Phlebotomus sandflies of Indiana type vesicular stomatitis virus and of the apparently new agent.

Field and laboratory tests of 2,2,4-trimethyl-1,3-pentanediol (TMPD) as a personal repellent were conducted against the black salt-marsh mosquito, Aedes taeniorhynchus (Wiedemann), in Grand Cayman Island, British West Indies; snowpool Aedes and Culiseta in Alaska; Culex and Anopheles in Jamaica, West Indies; blackflies (Simuliidae) in New York; the chigger Eutrombicula alfreddugesi (Oudemans) and the oriental rat flea, Xenopsylla cheopis (Rothschild), in Florida; and the lone star tick, Amblyomma americanum (L.), in North Carolina. Deet was used as a comparative standard, The results indicated that TMPD at strength equal to deet rates in effectiveness approximately 0.66–1.05 when deet is 1.00.

Much of the recent epidemiological work on human malaria and Anopheles has pointed to a need for more knowledge of the races of mosquitoes involved as well as of the parasites. Although much has been done in morphological, physiological, ecological, and biometric studies on the Anopheles mosquitoes, there have been serious drawbacks to genetic research with Anopheles because of their eurygamous habits; because individual selections and matings, so important in genetic work, are practically impossible; and because of the expense involved in housing them properly. In order to circumvent some of these difficulties a Culex mosquito was chosen for this study. Culex pipiens is relatively easy to maintain in the laboratory due to the existence of a stenogamous race in which individual matings after selection can be made. The particular one chosen and used throughout was a stenogamous and autogenous race. Any advances of biological significance made in the study of the species Culex pipiens may be related to the general problem of bird malaria. This in turn may serve as a foundation for similar observations within the field of human malaria.

Evidence of blood meals and ovarian development in female C. tarsalis is more apparent in this area during February and March than during the normal season of lessened activity (overwintering) from November to January. Males ordinarily are first found in early April, following the appearance of larvae during March in rain and irrigation water. As compared with other Culex species, C. tarsalis is found in larger proportion in natural (animal burrow and tree-type) habitats than in artificial ones (chicken houses, cellars, and bridges) Major population peaks of adult C. tarsalis were in June, July, or August in artificial resting places, in August or September in natural ones, and in July or August in light-trap collections. For measuring mosquito populations in artificial resting places, the use of 1-cubic-foot cardboard boxes proved as reliable as 10-minute collections and 5-minute estimates. Data are also presented on occurrence of blood-fed and gravid individuals and seasonal abundance of C. pipiens, C. stigmatosoma, and Anopheles freeborni, as they were observed during this 3-year study.

Each of two analogues of insect growth hormone (22-isoecdysone and ecdysterone) stimulates vitellogenesis in Aedes aegypti, whereas two synthetic juvenile hormone preparations (a terpenoid mixture and Cecropia hormone) do not. Development of oocytes is not affected by three diverse steroids (cholesterol, hydrocortisone, and estriole) or by phagostimulants normally present in vertebrate blood (ATP, serum, and haemoglobin). Two observations indicate that ecdysterone affects the ovary directly. Yolk is deposited when abdomens are ligated immediately after injection of hormone. Oocytes in excised ovaries pinocytose peroxidase from hormone-containing incubation media. Eggs mature after female A. aegypti, Culex pipiens, or Anopheles quadrimaculatus imbibe ecdysterone ad lib. However, relatively few eggs are deposited; most ovarian follicles degenerate. Such mature eggs are viable and give rise to normal anautogenous adult mosquitoes.

Buzz-z-z-z-z-z-z Swat! How often these sounds are re-enacted during warm summer evenings, together with a condemnation of mosquitoes in general and the ones at hand in particular. Although mosquitoes long have plagued mankind as vectors of disease and just plain spoilers of outdoor fun, there is one area in which they can be of some value. This is in the high school biology laboratory. Using the mosquito has several important advantages. Its short life cycle makes it possible to study complete insect metamorphosis usually within the time spent in class on insects. Ten to 14 days is enough time to obtain adults from eggs. By using a hand lens or microscope, the student can watch the larvae wriggling free of the egg cases during hatching. The development of the larvae through the four larval stages can be observed, as can the process of pupation. During the pupal stage the development of the adult structures can be seen through the cuticle. By watching from the first day of pupation, the formation of the adult can be followed. At the end of this stage it is a fascinating sight to see an adult mosquito emerge from its pupal case, dry its wings, and leave the water. All this in two weeks or less. Almost any species of mosquito will do. In the spring students can collect eggs and larvae of several species of Culex and Aedes. Through most of the United States, the most commonly found are Culex pipiens, Aedes vexans, and Aedes stimulans. Culex pipiens, the common house mosquito, breeds in stagnant water almost anywhere. The latter two are floodwater mosquitoes-the eggs being laid on land, and hatching when rising water covers them. Woodland pools are common collecting places for these species. Rafts of Culex eggs can be obtained commercially from any one of several biological supply houses any time during the year. The illustration shows the chief differences between A edes and Culex, as well as the main characteristics of the Anophelines. The mosquito is a useful animal in studying genetics. It is larger than Drosophila and has a high spontaneous mutation rate. Many of these mutants are visible with the naked eye. Although most mutations have been found in adults, some can be observed in the larvae. Mendel's Laws can easily be demonstrated with the mosquito, and long term genetic studies by individual students can produce excellent projects. Probably the best laboratory species is the yellow fever mosquito, Aedes aegypti. Its use should be confined to the northern states, however, as the south is its natural habitat. Eradication is the order of the day in that area. In the laboratory A. aegypti has the advantage of laying its eggs on paper towelling which can be stored. Hatching and rearing then can take place at any time. This species is commonly reared in medical schools and biological laboratories. In rearing mosquitoes the temperature should be between 70-90?F with 80?F producing the best results. Humidity should be between 50 and 95%o. At 80?F and 80% relative humidity adults can be produced in 7-9 days with proper feeding (see Table 1). At ordinary room temperature it takes closer to two weeks. Lighting is not a factor, as development will take place in total darkness or 24 hour light. Under laboratory conditions A. aegypti will lay its eggs in a container just above the water line-not on the water. The container should be lined with paper towelling to provide a place for oviposition. This will usually be completed four days following the blood meal. The towelling is then removed from the container and allowed to dry slowly. The eggs can be stored and will stay viable for several weeks. The eggs of

This study has demonstrated that Japanese encephalitis virus multiplies readily within Culex gelidus and that this mosquito is capable of transmitting the virus to susceptible hosts. The minimal concentration of virus capable of infecting this species was found to be four LD50 per 0.03 ml. of blood. The minimal viral incubation period observed in C. gelidus was 6 days. It was shown that as the dosage of virus ingested by the mosquito increased, the transmission rate also increased, but the length of minimal incubation period decreased. C. gelidus transmitted virus as effectively by probing the host animal as by feeding to repletion. More than one host could be infected by a single infective mosquito in a short period of time if the mosquito was interrupted during the act of feeding. Transmissions of virus by a single infected mosquito were obtained as often as four times in 2 weeks. Attempts to demonstrate mechanical transmission of virus by C. gelidus were negative, as were efforts to obtain transovarian passage of virus by this mosquito. The demonstration of the efficiency with which this mosquito transmits the virus under controlled conditions, combined with evidence from field studies, provides the data necessary to incriminate C. gelidus as an important vector of Japanese encephalitis.

The paper describes a method for staining the phosphate moiety of phospho-proteins after electrophoresis on polyacrylamide gels. The method depends on hydrolysis of the phospho-protein phosphoester linkage using dilute base in the presence of calcium ions. The gel containing the newly formed insoluble calcium phosphate is then treated with ammonium molybdate in dilute nitric acid. The resultant insoluble nitrophospho-molybdate complex is finally stained with the basic dye, methyl green, dissolved in dilute acetic acid. After destaining, a green band is observed on the gel at the locus of the phospho-protein. One nanomole of protein-bound phosphate is detectable.