Seasonal fluctuation of larvae of trombiculid mites on small rodents in the wind-shelterbelt at Tonden, Sapporo

Abstract

A survey of trombiculid mites found on the small rodents was carried out in the windshelterbelt at Tonden, Sapporo, through a year from June 1973 to June 1974. From 239 rodents consisting of five species, a total of 41,961 trombiculid larvae was collected, of which 91.6% were Leptotrombidium (Leptotrombidium) intermedium, 7.7% were Neotrombicula tamiyai, 0.3% were N. japonica, and 0.4% were Gahrliepia (Gahrliepia) saduski. Among them, N. tamiyai is new record for the central Hokkaido. Seasonal fluctuations of larvae of trombiculid mites are shown in Fig. 1 and Table 2. The difference in the average number of the mites was observed among the hosts. In a descending scale, as follows; Clethrionomys rufocanus>C. rutilus>Rattus norvegicus>Apodemus giliacus and A. argenteus. And also, the difference of the modes for attachment to a host was observed among the species of the mites; L. intermedium and N. tamiyai were mainly found in the ear conch of the rodents, and, G. saduski and N. japonica, which presented the elevated volcano-shaped wheals at the attached sites, on the hind body region. Making reference to the previous reports in Hokkaido, the present study revealed that L. intermedium, N. japonica and G. saduski are found in all vegetations (Table 3). Generally, according as vegetation is simplified, species number of the mites is decreased and, to the contrary, the average number per host is increased.