Nutritional sensitivity of fifth instar prothoracic glands in the tobacco hornworm, Manduca sexta.

Insulin-regulated growth of the prothoracic glands appears to play a critical role in timing the last larval molt, and hence metamorphosis. The present study examined insulin signaling in relation to the growth and secretory activity of prothoracic glands in the tobacco hornworm, Manduca sexta. As larvae feed during the first half of the final larval stage, the prothoracic glands grow and ecdysone secretory capacity increases.