準自然域におけるショウジョウバエ集団の研究〔英文〕-2-

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Collections of Drosophilidae were made by trapping each month from May to October during the period of 1956 through 1962 in the University Botanical Gardens.Drosophila auraria was found to dominate over the other species collected, showing 40.08%. Ninety-three percent of the auraria population was occupied by race A.The race A showed usually a unimodal activity with a single peak in the middle of summer. However, a bimodal activity occurred in 1958 and 1960 with a small peak in May and a large one in July or August.The frequency of females in the entire sample of this race was 48.39%. The value would have been more than fifty percent, if collections would have been made in the same way in 1959 as in the other years. Because, variations in sex-ratio were found in 1959 populations sampled from different places and lures, and at different times. There was, however, a general tendency that the frequency of females of this race was inversely related to the population activity.