Distribution and seasonal prevalence of the malaria vector mosquito, Anopheles minimus, in Ishigaki Is., Ryukyu Archipelago, Japan, 1990-1994

To confirm the density and seasonal prevalence of Anopheles minimus, and chemical characteristics of its larval habitats, surveys in 30 streams were carried out in Ishigaki Is. of the Ryukyu Archipelago from 1990 to 1994. The larvae and pupae of An. minimus were collected in 20 out of 30 streams. This species is widely distributed throughout Ishigaki Island except the urban area. High density of immatures on the coastal forests in north and low density in farmlands on the central area were observed. The water quality of streams where many immatures of An. minimus were found was relatively clean. The number of An. minimus immatures increased gradually from April and peaked in July to September. From November, the population gradually decreased to the lowest in March.