In order to be in quest of the biochemical basis of photoperiodic induction on diapause of the cotton bollworm Heliothis armigera Hubner, the present study deals with the following aspects:1. The levels of the cyclic nucleotides, which have been demonstrated as the second messenger of the polypeptide hormones and the neurotransmitters, in the course of the photoperiodic induction on the diapause of the bollworm Heliothis armigera Hubner were studied.2. The levels of the cyclic nucleotides in the brain and t...