Abstract: Diapause hormone (DH) is a neurohormone which is secreted from suboesophageal ganglion and responsible for induction of embryonic diapause in Bombyx mori.Here,using bioassay,we present evidence that Has-SGNPⅠ,which clearly exhibited diapause egg inducing activity as does Bom-DH,is likely to be DH.We reported the molecular characterization of the Helicoverpa assulta diapause hormone analog by polymerase chain reaction.A 665 bp fragment containing the entire DH-like gene was isolated and characterized.DH-like gene comprised two exons interspersed by a single intron,and the consensus sequence for splicing junction is identified at the exon/intron boundary.The result shows that DH-like gene is localized in the genome of Helicoverpa assulta.