Abstract
Field surveys were made on the ectoparasite of the wood mice at KARAO-valley, HIROKAWA-cho, ARITA-gun, WAKAYAMA-ken, JAPAN, through a year from July 1954 to June 1955. In the present paper, as a part of these surveys, we report on the seasonal fluctuations of the population of chigger mites and their species complex. The results are as follows; 1. Throughout these surveys, 59 individuals of mice as host and 5281 individuals of chiggers of 9 different species as ectoparasites are captured. 2. We can divide following three types in the seasonal fluctuations of their populations which are represented by the mean numbers of the collected chiggers per one host. A. During the all seasons can be caught, but few. Trombicula kansai, Gahrliepia suduski. B. The mode of population appeares in November or December. T. kitasatoi, T. pallida, T. miyajimai. T. japonica. C. The mode of population appears in January or February. T. fuji, T. kochiensis, T. daisen. 3. Chigger fauna at the different area does not differ significantly. 4. Average number of the rankings of abundance of each species on the whole individuals of captured mice (Ranking index), does not always change in parallel with the mean of population density of each species. 5. By the difference of fluctuation of the rankings of abundance of each chigger, the species complex of mites on each mouse can be divided into following three types; A. Standard deviation of the ranking is always smaller than 1 T. fuji, T. kochiensis. B. Standard deviation of the ranking varies from 0 to 2 T. kitasatoi, T. pallida, G. suduski. C. Standard deviation of the ranking is always larger than 1 T. daisen, T. kansai, T. miyajimai, T. japonica. 6. The correlation between the body weight of the host and collected number of the chiggers is highly significant, and its correlation coefficient is +0.602.
