Activation of the Prothoracic Glands of Antheraea polyphemus

Abstract

EVIDENCE has accumulated that the moulting cycle in insects follows a basic pattern involving the activation of the prothoracic glands by a hormone from the brain. The active prothoracic glands then secrete into the blood the moulting hormone, ecdysone. Secretion of the brain hormone has therefore been thought critical in the induction of moulting. The central role of the brain is particularly evident in animals with a pupal diapause, where adult development is not initiated if the prothoracic glands are not activated. Many experiments^1,2 have shown that the brain of the diapausing saturniid pupae can be activated by exposing the pupae for various periods to temperatures of less than 10° C. The present investigation confirms the additional observation of Williams (unpublished work) that the brain may be activated by surgical means not involving chilling, and suggests that in certain circumstances the prothoracic glands are activated without the mediation of the brain.