ABSTRACT

The testes of Lepidoptera are usually ovoid, paired organs suspended in the abdominal cavity. The sheath surrounding each testis has prominent cellular layers. Release of sperm from the testis to the male genital tract in adult male Lepidoptera is negatively controlled by ecdysteroid. Testes of late-last instar larvae were separated into components by gentle teasing and agitation in Ringer solution. Methanol extracts of brains of late-last instar and midpupal male Heliothis Virescens, incubated with testes of early-last instar larvae, and initiated ecdysteroid production in the normally inactive organs. Isolated sheaths from late-last instar testes, which normally produce ecdysteroid spontaneously in vitro, showed a startling dose-dependent positive response to exogenous 20- hydroxyecdysone. Young testes, which do not normally produce ecdysteroid spontaneously in vitro, were not affected by exogenous ecdysteroids, although they could be stimulated to produce immunodetectable ecdysteroids after exposure to testis ecdysiotropin.