Abstract
After the treatment of insecticides to female cockroaches, Blattella germanica L., by contact method, topical application method and injection method, observations were made on the dropping of egg capsules, the hatching rate of the eggs and the mortality of their lst stage nymphs. All capsules were dropped after knockdown of the maternal roaches by the treatments of dieldrin, chlordane, diazinon, DDVP and dibrom. Though the knockdown time of the roaches treated with dieldrin and chlordane was nearly equivalent, the time of dropping of egg capsules was faster in dieldrin than in chlordane. This may be ascribed to the difference of insecticidal mechanism in these two chemicals. Hatching of the eggs laid by the roaches treated with the above mentioned five chemicals were seen only within 5 to 10 days after their capsules dropped, but no hatching was seen later. The nymphs from the roaches treated with DDVP and dibrom survived normally, and those from the roaches treated with diazinon, chlordane and dieldrin took two courses : the one died within 4 days entirely or partly after hatching and the other survived normally.
