Endocrinological adaptations in insects

Summary Insect larvae respond differently to juvenoid treatment. Larvae occurring in relatively constant ecological conditions with abundant food, e.g.Trogoderma granarium, Tribolium castaneum, Corcyra cephalonica andEphestia cautella, can undergo several extra larval moults, show growth with each moult, may moult 2–3 times with 1 treatment and do not suffer ecdysial failure. Larvae adapted to changing ecological conditions, e.g.Spodoptera litura, Earias fabia, Papilio demoleus, Euxoa spinifera andAttacus ricini, rarely undergo supernumerary moults, and the supernumerary instars suffer from ecdysial failure. It is suggested that the former have evolved an endocrinological adaptation.Acknowledgment. We express our thanks to the Indian National Science Academy, New Delhi, for financial assistance to USS in the form a project grant and the Zoecon Corporation, California and Dr. R. Maag Ltd, Dielsdorf, Zurich for gift of juvenoids.