Abstract
Larval moult before and after the penultimate instar (5th instar) in Leucania separata involves an endocrine cascade that begins with the release of PTTH. The mechanism of this process is as follows : the newly ecdysed 5th instar larvae weighting average 44.0 mg have been already destined to release PTTH at Gate II stage (just before the 3rd night), and subsequently the released PTTH activates the prothoracic glands to increase the hemolymph ecdysteroid titer. The head capsule slippage is induced by this ecdysteroid surge. The 6th instar moult is finally observed about 20 hr after the head capsule slippage. The entire process of this endocrine cascade from 5th instar larva to last instar takes 3 days.
