This review aims to identify the factors, both genetic and nongenetic, which influence the susceptibility of mosquitoes to malaria parasites. The paper is divided into three sections. In the first, genetic differences in susceptibility between and within mosquito species, and mechanisms of refractoriness are discussed. In the second section, the effect of phenotypic factors such as mosquito size, blood digestion, nutrition, and the presence of other parasites are assessed. In the third section, the influence of insecticides and drugs is summarized.

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Seasonal prevalence of a nuisance sphaerocerid fly, Leptocera fuscipennis (Haliday), was investigated using light traps placed both at breeding sites of the fly in the sewage sludge disposal site of Haneda (Tokyo International) Airport and at residential areas near the airport from May to November 1979. Frequent complaints from residents about flies had been made during the preceding two years. Therefore in 1979,619,000m^3 of sea water was applied to the breeding sites in total of 5 times from June 20 to July 27 to control flies before their mass breeding season. A large number of flies were captured in July and September at the breeding sites. Concentrated dispersal of flies to human dwellings occurred only in July. This happened at the end of rainy season between sunset and midnight when a northeast to southeast prevailing wind of 10-15m/sec blew. The number of flies captured in the residential areas, however, were far less than in preceding years and no more complaints were received from residents.

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The expression of autogeny of Simulium aureohirtum Brunetti among three populations in the Ryukyu Islands was examined by maintaining newly emerged females on or without a sucrose solution. Mature eggs were produced only in the females fed on sucrose as early as three days after emergence at a temperature of 20℃. The mean maturity rate per fly was around 90%. Maturation of ovaries also occurred when flies were given a sucrose solution after one, two and three days of starvation. However, due to the increase in resorbing follicles, maturity rates were greatly decreased, especially after two and three days of starvation (to around 60-70%). Moreover, development time was retarded one day, as compared to that in flies fed on sucrose from the time of emergence. Fecundity (the number of mature oocytes per fly) was found to be positively correlated to the wing size within a population. However, the mean fecundity was not necessarily related to the mean wing size when different populations were compared.

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Flies of the genus Coproica are recorded from Taiwan and Hong Kong. Five species from Taiwan and 4 species from Hong Kong are newly recorded. The following 4 species are recorded from the Oriental region for the first time : Coproica acutangula (Zetterstedt, 1847), C. coreana Papp, 1979,C. hirticula Collin, 1956 and C. lugubris (Haliday, 1836).

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A year-round survey of chironomid midges was carried out using light traps at Lake Kojima in Okayama Prefecture from July 1985 to December 1986. The final collection site was selected from preliminary collections at 5 spots from July 8 to 9,1985. The annual total of the monthly mean numbers of the collected midges was 41,669 (male 15,795; female 25,874). Twenty-one species of 15 genera were collected, and the major species were Polypedilum arundinetum (14,254), Parachironomus arcuatus (5,234), Microchironomus ishii (4,622), Tanytarsus oyamai (4,057), Chironomus kiiensis (3,004), Tanypus punctipennis (2,490), Pentapedilum tigrinum (2,349), Polypedilum masudai (1,577), Polypedilum nubifer (980), Dicrotendipes niveicaudus (962), Cricotopus sylvestris (936), and Tokunaga-yusurika akamusi (526). Many species of adult midges emerged from June to September. Some species were abundant in the winter, and one species (Limnophyes hudsoni) showed two peaks in its prevalence, in spring and autumn.

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Tabanid flies were collected with CO_2-lured mosquito-net traps at horse breeding farms in Shiraoi and Mukawa of Iburi District, Hokkaido, from mid-July to late August in 1980. Flies which attacked horses were counted at the same time. Sixteen species belonging to 6 genera were recorded in total, 12 species in Shiraoi and 14 in Mukawa. Tabanus nipponicus was the predominant species accounting for 72.5% followed by Atylotus horvathi and T. katoi in Shiraoi, and 33.8% followed by T. fulvimedioides, A. horvathi and T. sapporoenus in Mukawa. Flies were more abundant in early or late August than in mid-July seasonally, and more numerous in Mukawa than in Shiraoi locally : more than twice as many were trapped at the latter location. Diurnal fluctuations in the catch of flies between 9 : 00 and 17 : 00 were relatively small in Shiraoi, while the peak of activity was clearly observed between 9 : 00 and 12 : 00 in Mukawa. The number of flies trapped correlated with the number of flies which attacked horses.

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Irritability tests of Anopheles farauti to permethrin were carried out at Honiara, Solomon Islands in September 1985 and of An. maculatus and Culex quinquefasciatus to permethrin and DDT in Kuala Lumpur, Malaysia in January 1986,applying the WHO Expert Committee methods with some modifications. An. farauti and Cx. quinquefasciatus showed a high degree of irritability (the response to external stimuli) to permethrin, averaging respectively 6.5 and 7.4 times higher than the control. An. maculatus showed a lower level of irritability to permethrin, averaging 2.7 times higher than the control. A graded response to increasing dosages of permethrin was shown by An. maculatus, but not by the other species.

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Five species of the cockroaches were captured from the so-called Yambaru area of Okinawa Island. Two of them, Anaplectella ruficollis (Karny) and Trichoblatta pygmaea (Karny) are new additions to the fauna of Okinawa Island.

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[in Japanese]

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Fourteen egg-batches of Hybomitra distinguenda (Verrall, 1909) were collected from 3 marsh plants, mainly Carex vesicaria L., in sunny places in Hokkaido from mid-July to early August. The eggs were laid on rather narrow and almost vertical leaves at an average height of 48.4cm above the water surface. The egg-batches were enamelled black in color, consisting of an average of 224 eggs, and elongate-flat in shape with 1 to 3 layers of eggs. Three egg-batches of Hy. takahasii Inaoka et Hayakawa, 1982 were collected from one marsh plant, Carex amplifolia, in shaded areas in Hokkaido in mid-August. The eggs were laid on rather narrow and upward-slanting leaves 49.7cm above the water surface. The egg-batches were black in color covered partly by greyish dust at the tips of the eggs, consisting of an average of 192 eggs, and roughly disk-like in shape with 2 to 3 layers of eggs. The eggs of Hy. takahasii were parasitized by wasps, but not those of Hy. distinguenda.

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[in Japanese]

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