In a previous study, allatotropic and allatostatic activities were observed in brain extract from the Eri silkworm, Samia cynthia ricini (Samcri) [Li, S., Jiang, R.-J., Cao, M.-X., 2002b. Allatotropic and allatostatic activities in brain extracts of the Eri silkworm, S. cynthia ricini, and the effects of Manduca sexta allatotropin and M. sexta allatostatin on juvenile hormone in vitro. Physiol. Entomol. 27, 322-329]. In the present study, the HPLC purified Samcri-allatotropin (AT) and -allatostatin (AST) factors were shown to have the same retention time as those of M. sexta (Manse)-AT and -AST, respectively. Moreover, the amino acid sequences of mature Samcri-AT and -AST deduced from their encoding cDNAs are identical to the Manse-AT and -AST amino acid sequences. Both Samcri-AT and -AST genes were expressed in brain, nerve cord, and midgut, with Samcri-AT also detected in gonads and epidermis, suggesting their pleiotropic physiological functions. The expression levels of Samcri-AT and -AST genes correlated well with the allatoregulatory activities during the period of adult emergence indicating the two peptides tightly control JH synthesis, in a contradictive and cooperative manner. Our biochemical and molecular data of Samcri-AT and -AST and other studies demonstrate that these two peptides regulate JH synthesis by corpora allata in Lepidoptera and have pleiotropic physiological effects.