Ecology of vector mosquitoes of Japanese encephalitis, especially of Culex tritaeniorhynchus. 1. Results obtained in 1965.

The ecology of vector mosquitoes of Japanese Encephalitis is essential to obtain a satisfactory understanding of the epidemiology of the disease. In this connection, the relative abundance, host preference, and seasonal history of the mosquitoes in Nagasaki area were investigated in 1965. Culex tritaeniorhynchus is a most abundant species in farm villages, and is strongly zoophilic. The overwintered females begin to appear in late March or early April; adults of both sexes originated from them appear in middle or late May; the population density thereafter is nearly unchanged until the maximum period in density from middle July to late August; the number of mosquitoes decreases abruptly in early September and thereafter a very small number of them are only collected till early October. The day length seems to be a controlling factor in determining the gonoactivity of the females of C. tritaeniorhynchus rather than the temperature under certain conditions. The seasonal prevalence of this mosquito is compared also with those of the other four dominant species, Culex vishnui, Aedes vexans nipponii, Armigeres subalbatus and Anopheles sinensis.