For the purposeof examining DDT influences to fruit-filies, Drosophila Melanogaster , authors observed the number of eggs laid and hatching rate of them treated with various concentrations of DDT. The results obtained were summarized as follows : 1. There was a significant difference between treated and non-treated groups in the number of eggs laid. 2. The number of eggs laid in the treated groups was gradually decreased as the DDT-concentration increases. 3. The hatching rate of the treated larvae was not significantly different from that of the non-treated , while a distinct difference between treated group and non-treated one was seen when DDT treatment was given to the adults. 4. The average number of eggs laid by a non-treated fly for 15 days was 216. The curves for the number of eggs laid in both the treated and non-treated groups for 15 days revealed almost similar patterns, although the treated groups laid the largest : number of eggs in the forth day, while in the non-treated one it is seen in the sixth day after counting eggs.