PHYSIOLOGY OF INSECT DIAPAUSE. XIV. AN ENDOCRINE MECHANISM FOR THE PHOTOPERIODIC CONTROL OF PUPAL DIAPAUSE IN THE OAK SILKWORM, ANTHERAEA PERNYI

Abstract

1. In the oak silkworm,Antheraea pernyi, photoperiod controls not only the onset of pupal diapause (as previously demonstrated by Tanaka) but also the termination of pupal diapause.2. At 25° C., short-day conditions (4-to 12-hour photophases) strongly inhibit the termination of pupal diapause; maximal inhibition is by a 12-hour photophase.3. Long-day conditions (15-to 18-hour photophases) promote the termination of diapause; a 17-hour photophase is the most effective.4. A 14-hour photophase is transitional between short-days which sustain diapause and long-days which terminate diapause.5. By various experimental maneuvers, sensitivity to photoperiod was localized in the head-end of the pupa. Short-day illumination of the head-end inhibited the termination of diapause even when the hind-end was exposed to long-day conditions. In like manner, long-day illumination of the head-end was fully effective even when the abdomen received short-day illumination.6. When the brain was removed from the head and implant...