Haemolymph ecdysteroid levels in diapause-and nondiapause-bound fourth and fifth instars and in pupae of the European corn borer, Ostrinia nubilalis H übner

Abstract

1. 1. Diapause-inducing conditions had no effect on premolt peak ecdysteroid titers of penultimate stage European corn borer larvae. 2. 2. Haemolymph ecdysteroid titers of pharate fifth instars decreased more slowly in diapause-than in nondiapause-bound animals. 3. 3. Four haemolymph ecdysteroid peaks were detected during the last instar in nondiapause-bound larvae, the second of which was associated with a change from larval to pupal commitment. 4. 4. Pupae exhibited a major haemolymph ecdysteroid peak just prior to pharate adult formation; the gradual decline in ecdysteroid titers that followed was interrupted by two significant peaks in males and one in females. 5. 5. There may be many more significant ecdysteroid surges than was originally thought controlling a variety of developmental processes during the insect life cycle.