Adult Diapause of the Fleabeetle, Argopistes biplagiatus MOTSCHULSKY (Coleoptera: Chrysomelidae)

I. Seasonal Trends in Feeding and Oviposition Activities

Abstract

Under field conditions, newly-emerged adults of Argopistes biplagiatus show a high feeding activity in early summer, but it soon declines and stays at a low level during mid-to-late summer. In early autumn, the feeding activity increases again and stays at a high level until late autumn. After hibernation, feeding is resumed in early spring with a peak in May. From early to mid-summer, overwintered adults feed little on host leaves but their activity increases again in early autumn. Under field conditions, oviposition was observed only in spring (from March to May). Newlyemerged females collected from early summer to autumn never laid eggs under long (15L-9D) or short (12L-12D) photoperiod at 20°C. However, most females collected from late autumn to midwinter deposited eggs under long day conditions but not under short days. In early spring, they deposited eggs under both long and short days. This regulation mechanism possibly enhances the synchronicity of the oviposition period with the start of host-plant sprouting.