Abstract
Adults of Henosepilachna vigintioctopunctata enter diapause under short-day photoperiods, while they become reproductive under long-day conditions. When JH-I or JHA (ZR-515) was applied on the beetle under diapause-inducing cnoditions, the ovaries began to develop, but the last stage of yolk deposition and the chorion formation did not occur even at high dosages. Number of oocytes in a vitellarium of the ovarioles of treated animals tended to increase to 4 whereas normal ovarioles contained 3 oocytes at most. Of the insecticides tested, pyrethroids such as cypermethrin and flucythrinate showed stimulating effect on the ovarian development, and partly induced oocyte maturation and oviposition.These results suggested that two endocrine factors, JH and neurosecretory factor, were engaged in the control of ovarian development and that secretion of both factors was stimulated by the pyrethroid application.
