Environmental factors determining wing form in the lygaeid bug, Dimorphopterus japonicus (Heteroptera: Lygaeidae).

Abstract

Dimorphopterus japonicus, a lygaeid bug which mainly feeds on the eulalia, Miscanthus sinensis, shows a marked wing dimorphism of brachyptery and macroptery. Our preliminary experiments suggested that temperature, photoperiod and density during the nymphal stage are important for the determination of wing form in D. japonicus. The purpose of this study was to elucidate, by more detailed experimentation, the relationships between each environmental factor and the incidence of macroptery. Environmental factors such as high temperature, long photoperiod, and crowding during the nymphal stage stimulated the production of macropters in D. japonicus. Moreover, the incidence of macroptery increased with increase in temperature, photoperiod and density. Results that no macropters appeared at a density of 1, 2 and 5 individuals per container, might indicate that body contact among bugs is necessary for macropter development and the fact that the incidence of macroptery increased, depending on crowding, is suggestive of a strategy for escape from deteriorating habitats. Moreover, both conspecific crowding and seasonal factors, such as temperature and photoperiod, were important in the determination of wing form. The strong effect of seasonal factors such as temperature and photoperiod on wing-form determination implies that wing dimorphism has evolved as a component of seasonal adaptation.