Effects of the Insect Growth Inhibitor, Dimilin,® on Hatching of Mosquito Eggs

Exposure of egg rafts of the southern house mosquito, Culex pipiens quinquefasciatus Say, to water treated with Dimilin® [1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)-urea] induced abnormal side-hatching as well as ovicidal action. The activity was influenced by the age of the embryos at the time of treatment; younger embryos (preblastoderm stage) were the most sensitive and 7-, to 23-h-old embryos were more tolerant. The side-hatching and ovicidal phenomena also were produced by baiting adults with Dimilin in sucrose. In this instance, females were more sensitive than males. Ovicidal and abnormal hatching due to baiting with Dimilin was likewise exhibited in Culex tarsalis Coquillett and Aedes taeniorhynchus (Wiedemann).