A great occurrence of Drosophila virilis in the neighborhood of a lumberyard in Niigata City

Abstract

There was a great occurrence of Drosophila virilis after the rainy season of 1960 in the neighborhood of a lumberyard in Niigata City. Great number of flies entered into human dwellings and afflicted the people. We found many larvae and pupae under the bark of Siberian spruce, fir trees, larch and white birch which had been landed and stored in the lumberyard. The distribution and population density of the adults were examined by means of the fly catch ribbon, and the results are summarized in Table 1. Number of flies captured within 200m from the lumberyard is greater than that of flies captured in the distance of more than 200m away from the lumberyard. DDVP (0.3% kerosene solution) and BHC (1.5% powder) were spreaded directly on their habitat and only DDVP was fogged in rooms of human dwellings. The results are summarized in Table 2. The decrease of the adults might be seen in the house where DDVP was fogged. It is difficult to estimate the actual effect of insecticides, however, we have only described hereby the results obtained.