Trombicula akamushi (Brumpt, 1910) 未吸着幼虫の日週活動について

抄録

In the summer of 1954, the observation on the diurnal rhythmic activity of the unattached larvae of Trombicula akamushi (Brumpt, 1910), the vector of Tsutsugamushi disease, was made in a certain wood along the Omono River in northwestern Honshu, Japan. The number of the mites crawled up on nine black bakelite-plates, which had been set on the ground surface two days before the observation, was counted every hour for 37 and 11 consecutive hours. Four counts were made in each hourly observation at intervals of five minutes. According to the results, the mite count was the highest at 3 : 00 or 4 : 00 P.M. and a less inconspicious increase was seen at 11.00 A.M. In the night time from 7 : 00 P.M. to 6 : 00 A.M., the mites seemed to be much less active than in the daytime. Such environmental factors as the air temperature and the relative humidity 2cm above the plate, the soil temperature 10cm beneath the soil surface and the light intensity on the plates were measured at each time of the counts. It was revealed that the number of the mites observed on the plates showed significant positive correlation to the soil temperature or the light intensity, and significant negative correlation to the relative humidity, but that between the number of the mites and the air temperature was not significant. Among the numbers of the mites in four counts at each observation, the first counts were usually the lowest, and was the highest the last counts. The difference between average numbers of the first and the second, and that between the second and the third were statistically significant, but that between the third and the fourth was not significant.