Diapause development in the tobacco hornworm: A role for ecdysone or juvenile hormone?

Abstract

Injection of a moderate dose of 20-hydroxy-ecdysone (20-HE) or a large dose of juvenile hormone analog leads to prompt termination of diapause in pupae of the tobacco hornworm, Manduca sexta (Johannson). Both agents appear to exert their major stimulatory effect directly on the neuroendocrine system. There is little or no change in the 20-HE ED 50 during diapause development, and injection of a subthreshold dose of 20-HE does not alter the duration of diapause. Hemolymph juvenile hormone activity is indetectable in diapausing pupae, and allatectomy of young pupae does not affect diapause duration. Results are discussed in light of a possible role for ecdysone or juvenile hormone in diapause development.