Abstract: The ovarian structure as well as oogenesis is closely related with the accurate forecast of the pest occurrence peak and the appropriate control time. In order to make sense of the ovarian structure and oogenesis in the cotton bollworm, Helicoverpa armigera, we investigated both the ovarian structure and oogenesis of H. armigera female moth under the light microscopy and transmission electron microscopy, and determine the grading criteria to divide different developmental stages. According to the morphological characteristics of ovaries, the formation of eggs in the lateral oviducts and the characteristics of yolk deposition, the H. armigera ovaries are graded into 6 stages, including stage 0 (the initial stage), stage Ⅰ (yolk deposition prophase), stage Ⅱ (yolk deposition phase), stage Ⅲ (egg maturation phase), stage Ⅳ (peak phase of oviposition) and stage V (terminal phase of oviposition). According to the ultra-structural change of the oocytes and follicular cells, the developmental period of oogenesis is divided into 3 stages: the vitellogenesis prophase, vitellogenesis stage and yolk maturation stage. This study is the first research about oogenesis of H. armigera using electron microscopy, which optimizes the grading criteria of ovarian development of the cotton bollworm. The result provides an important theoretical basis for further study of reproductive development of H. armigera, and also has important practical meaning for the accurate forecast of outbreak date and scale in pest management.

Key words:  Helicoverpa armigera, ovary, morphology, ultrastructure, developmental stage, oogenesis