A comparison of the larval overwintering biology of the striped stem borer, Chilo suppressalis (Lepidoptera: Crambidae), in rice and water-oat fields

It has been suggested that the striped stem borer, Chilo suppressalis (Walker), has developed distinct populations inhabiting rice Oryza sativa (Linnaeus) and water-oats Zizania latifolia (Turcz). In this study, we compared several biological traits between overwintering larvae from rice and water-oat fields during the winter of 2010. The parasitism rate was significantly higher in the larvae that overwintered in the rice field than in those that overwintered in the water-oat field. The average body weight of overwintering larvae and the weight of 3-day-old pupae, as well as the number of eggs carried by adult females, were all significantly greater in the samples from the water-oat field. The diapause intensity, defined as the number of days required until pupation by overwintering larvae transferred to 25 A degrees C and L:D 16:8 h, decreased progressively from January to March but decreased more rapidly in the water-oat field. Our results demonstrate differences in the overwintering biology of C. suppressalis larvae from rice and water-oat fields. These differences may contribute to the differentiation and reproductive isolation between host-plant populations in this species.