STUDIES OF THE ECDYSIOTROPIC ACTIVITY OF JUVENILE HORMONE IN PUPAE OF THE TOBACCO HORNWORM, MANDUCA SEXTA

Topical administration of a juvenile hormone analog (JHA) to pupae of the tobacco hornworm accelerated the initiation of adult development and proved to be an ecdysiotropic stimulus even in the absence of the brain. Nevertheless, individuals developing in response to JHA were never normal. In fact, doses of JHA too low to accelerate development often provoked typical abnormalities in the resulting moths. Allatectomy of either diapause-destined or non-diapause pupae failed to alter the time course of adult development. In line with this finding, corpora allata (CA) from both diapause-destined and non-diapause pupae were without activity in two juvenile hormone (JH) bioassays. These results suggest that JH is not involved in the normal initiation of adult development. Indeed, it must be absent for normal development to proceed. Evidently, the ecdysiotropic effect of exogenous JH in pupae reflects a sensitivity to JH retained from the larval period.