The fertility of mosquitoes largely depends on a blood meal taken from host animals or humans. After feeding, the blood proteins are digested in the midgut to amino acids, which are then transferred into the hemolymph. Although absorbed amino acids are utilized as precursors for vitellogenin synthesis, these nutrients have other important effects upon mosquito oogenesis. First, the increase of amino acid concentration in the hemolymph after a blood meal may initiate and promote follicular development. For this activity, it is essential that amino acids increase in a balanced composition; lack of any one of the nutritionally-essential amino acids fails to initiate the development of follicles. Second, the number of follicles which are able to mature depends largely on the amount of available amino acids in terms of either concentration in the hemolymph or length of supply from the midgut. During a number of evolutionary steps, mosquitoes seem to have acquired a system to monitor available amino acids for efficient oogenesis.

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The insecticidal efficacy against Triatoma dimidiata and Rhodnius prolixus, the main vectors of Chagas' disease in Guatemala, was evaluated in six Guatemalan villages. A 0.075% lambda-cyhalothrine suspension was the most effective to both species when sprayed at 40ml/m^2 on the mud walls or 80ml/m^2 to straw thatched houses, followed by a 0.2% liquid or 1% powder of deltamethrin, 0.5% propoxur liquid or 0.5% diazinon suspension, spraying at 100ml/m^2,during 2 to 4 months following the treatment, as assessed by man-hour collection or a count of the spots of vector excrements on white papers placed on the walls. However, diazinon powder and fenitrothion suspension were less effective than the other insecticides for vector control. Deltamethrin powder and liquid caused ocular and nasal irritation to the sprayers and residents immediately after treatment and lambda-cyhalothrine caused less irritation. The permethrin smoking agent was not effective to Rh. prolixus bacause smoke could not stay in the houses. We recommend the use of lambdacyhalothrine suspension in the Guatemalan mud and straw thatched houses.

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We studied the relationship between environmental conditions of open drains and the density of Culex quinquefasciatus Say immatures in Ujung Pandang, the biggest city in Sulawesi Island. Fifty sites in the 6 drains varied in environmental conditions such as the water flow, surface-water coverage, waste water input and the presence or absence of the larvivorous fish, guppy (Poecilia reticulata Peters). The immatures of Cx. quinquefasciatus were absent in all of the sites where the surface water flowed well. Among sites with stagnant surface water, the density of the immatures was high in the sites that received waste water. The mosquito immatures were absent in the sites without waste water input where the guppy was present. Although the predation pressure of the guppy might partially prevent Cx. quinquefasciatus breeding in less polluted water, its role in controlling the entire Cx. quinquefasciatus population in Ujung Pandang was considered to be small, because the guppy was absent in the most of sites with polluted water and the majority of drains in the city received waste water from houses. Improvement of the water flow and reduction of the waste water input are considered as the effective control methods of Cx. quinquefasciatus population.

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Pinholes of several sizes were exposed to Indian meal moths, and larval invasion through the pinholes was examined under the laboratory cage conditions. Hatching larvae could not penetrate 0.020mm-thick polyethylene film with no pinholes. Pinholes of 0.398mm or 0.450mm diameter resulted in as many larvae found in the food container as those of 0.495mm diameter. Fewer larvae (less than 1/10 of those through pinholes of 0.495mm diameter) invaded food containers through pinholes of 0.293mm diameter, and no larvae invaded through 0.173mm pinholes. Even a single pinhole of 0.495mm diameter could attract half as many larvae as a container opening of 29.2mm diameter, demonstrating the importance of a single pinhole. No eggs were deposited through the pinholes even of 0.495mm diameter, the largest size tested.

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Frequencies of blood meals and survival rates of vector mosquitoes are important parameters influencing transmission efficiency of pathogens. We applied the time series analysis proposed by Holmes and Birley (1987) for estimation of gonotrophic cycle lengths and survival rates of Culex tritaeniorhynchus and Cx. gelidus, Japanese encephalitis (JE) vectors in Thailand. Females of these species were collected at a buffalo shed and a pigsty in a suburban area near Bangkok during 30 and 24 consecutive nights, respectively. Specimens were dissected daily to determine the parity status by tracheation of ovaries. In total, 17,482 Cx. tritaeniorhynchus and 13,011 Cx. gelidus females were caught, including 15 and 19% of parous individuals, respectively. The time series analysis for the data set collected at the buffalo shed yielded a gonotrophic cycle length of 5 days and a survival rate per cycle of 20% for Cx. tritaeniorhynchus and 8 days and 16% for Cx. gelidus. From these estimates, daily survival rates were calculated as 72% and 80% for Cx. tritaeniorhynchus and Cx. gelidus, respectively. However, the data set collected at the pigsty did not yield significant results. Holmes and Birley's (1987) method could be an effective tool in epidemiological studies for Japanese encephalitis vectors, but its applicability is influenced by conditions at collection sites.

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The fauna and distribution of the blackflies in Miyazaki Prefecture were studied based on the collections of larvae and pupae from streams and adults flying around the collectors, at 82 localities in spring of 1995. A total of 16,088 blackflies, 14,210 larvae (88.3% in total number), 1,855 pupae (11.5%) and 23 adults (0.1%), were collected at 80 sites. All these blackflies were classified into fifteen species of the genus Simulium Latreille and Prosimulium Roubaud. Two species, Prosimulium (Prosimulium) yezoense and Simulium (Nevermannia) subcostatum s. l. were newly recorded from Miyazaki Prefecture. The most abundant species was S. (Gnus) bidentatum (47.3% in total number), followed by S. (S.) japonicum (12.8%), S. (S.) arakawae (10.7%), S. (Nevermannia) uchidai (7.0%) and S. (Odagmia) aokii (6.6%). The most widely distributed species was S. (Gn.) bidentatum (58 sites), followed by S. (N.) uchidai (42 sites), S. (S.) rufibasis (36 sites), S. (S.) japonicum (35 sites), S. (S.) arakawae (30 sites) and S. (O.) aokii (29 sites).

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A preliminary investigation on blackfly fauna was carried out in four provinces of the northern parts of Vietnam. A total of nine species are identified, of which six are newly recorded from this country : i.e., Simulium (Gomphostilbia) asakoae Takaoka et Davies, S. (G.) inthanonense Takaoka et Suzuki, S. (Simulium) hirtinervis Edwards, S. (S.) malayense Takaoka et Davies, S. (S.) quinquestriatum Shiraki, and S. (S.) tani Takaoka et Davies. This brings the total number of black fly species in Vietnam to 13 species.

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[in Japanese]

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New distribution records of three rare aedine mosquitoes in temperate Japan were presented. Species included are Aedes riversi, Ae. watasei, and Ae. bekkui. All or two of these species were recorded from Takashima and Fukushima, respectively, islands in the Imari Bay, northwest Kyushu. Ae. riversi was recorded from southwest Shikoku.

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[in Japanese]

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[in Japanese]

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