Synchrony of juvenile hormone-sensitive periods for internal and external development in last-instar larvae of Oncopeltus fasciatus

Breakdown of the moulting glands in Oncopeltus can be completely inhibited by topical application of a juvenile hormone analogue prior to day 2 of the fifth instar, and partially inhibited by application prior to day 4. The analogue-sensitive period for the inhibition of external metamorphosis is very similar to that for the inhibition of cell death in the moulting glands. A decline in response to the analogue between days 2 and 4 is correlated with rising ecdysteroid levels in the haemolymph. That this rise in ecdysteroids may be responsible for termination of the juvenile hormone-sensitive period is suggested by premature loss of sensitivity to the analogue by the moulting glands following premature exposure to 20-hydroxyecdysone.