Sexual differences in diapause induction of the cotton bollworm, Helicoverpa armigera (Hb.)(Lepidoptera: Noctuidae).

Abstract

The induction and termination of pupal diapause of Helicoverpa armigera were examined in three local populations from Kagoshima, Okayama and Ishikawa in Japan. Pupae in diapause retained eyespots for much longer than non-diapause pupae, and for markedly diverse durations. Once eyespots disappeared at the end of diapause, the period required for development until eclosion was more or less constant at 18°C. In all experiments repeated twice under the same conditions, male pupae generally showed a high tendency to enter diapause while female pupae showed a slight and rather population-specific tendency towards diapause. This trait as well as the higher intensity of male pupal diapause and the shorter post-diapause period of females suggest that females emerge first in the field in spring. This feature was regarded to be potentially important for considering the life-history strategy of this cosmopolitan pest.