Seasonal occurrence of larval trombiculid mites and distribution of Leptotrombidium scutellare in residential area and farmland in Kagoshima Prefecture

Abstract

The seasonal occurrence of unfed larvae of trombiculid mites was surveyed in four fixed areas using Tullgren funnel method from June 1994 to May 1995. Eleven trombiculid species were collected from soil samples : Leptotrombidium scutellare, L. kuroshio, L. pallidum, L. kitasatoi, L. fuji, L. kansai, Neoschoengastia shiraii, Walchia ogatai, W. koshikiensis, Gahrliepia saduski and Doloisia sp., with L. scutellare, L. pallidum, and L. fuji being dominant species. L. scutellare occurred from October to February with a sharp peak in October and November. L. pallidum occurred from August to May with a broad peak in October to March. L. fuji occurred from October to April. As to the summer trombiculid fauna, L. pallidum was included among 7 constituent trombiculids, but L. scutellare was not. Consequently, tsutsugamushi disease is probably transmitted by L. scutellare and L. pallidum in late autumn and early winter, and by L. pallidum in other seasons. L. scutellare larvae were collected from grasslands, groves, gardens of the housing lots and farmlands mainly with a black cloth.