Abstract: Using CREB antibody, immunostaining was performed on the central nervous system (CNS) of silkworm, Bombyx mori. CREB immunoreactivity was distributed in some neurons of CNS in the larval and the pupal stages. The numbers of CREB immunopositive neurons decrease from the 5th instar to the pupation. CREB immunoreactivity was different between diapause producer and nondaipause producer of bivoltine strain. Many immunopositive neurons were found in the 5th instar larval brain of diapause producer, but not in the brain of nondiapause producer. These results indicate that CREB may be related to regulation of the development and the metamorphosis of silkworm, and may play some role in the diapause process induced by environments.

Key words: Bombyx mori, diapause, immunohistochemistry, CREB