Abstract: In this paper, the morphology and ultrastructure of genitalia of cotton bollworm Helicoverpa armigera were studied and compared with its sibling species (H. assulta and H. zea), the results indicated that: (1)In morphology, there was evident variation among individuals in the same population of cotton bollworm (CBW), but noobvious differentiation among the 17 geographic populations of CBW. The numbers of folding and large spines on vesica, and length/width of valve between CBW and its sibling species are partly overlap. (2)In ultrastructure, there was no obvious differentiation among individuals or geographic populations of CBW , but there were obvious differentiations between CBW and its sibling species in the aedeagus cornuti. The cornuti on aedeagus is a stable distinct character between CBW and its sibling species found newly by the authors.

Key words: Helicoverpa armigera, genitalia, ultrastructure, morphological comparison