Abstract
The critical period of the brain hormone (prothoracicotropic hormone) secretion for pupation was about 2 days before pupation in larvae destined for both nondiapause and diapause. Some day 4 larvae destined for nondiapause ecdysed to pupae even after neck ligation. The critical period of the brain hormone secretion for adult development varied in nondiapause pupae, while it became very uniform on chilling in diapause pupae. When a brain from a last-instar larva destined for nondiapause was implanted into a larva of the same stage destined for diapause, diapause was prevented after pupation.
