Abstract
The pyrrhocorid bug, Pyrrhocoris sibiricus, which is a ground-dwelling seedfeeder, shows a wing polymorphism producing brachyptery and macroptery. The present study was undertaken to clarify the seasonal variation in the incidence of macroptery in this species. Adults of this species were collected from a field in Okayama from July to December in 1994 and in 1995. Fifth stadium nymphs were also collected from the same field from September to October in 1995. The nymphs were reared at 25°C under 16L-8D. All adults were checked for wing form. It was indicated that the incidence of macroptery showed a seasonal variation in both sexes. In 1994, the incidence of macroptery was high from late August to mid October in females and from mid September to mid October in males. The incidence of macroptery was higher in September than in October in the adults which had emerged from the 5th stadium nymphs. These results indicate that the incidence of macroptery becomes highest in the early autumn. The incidence of macroptery in the autumn was higher in 1994 than in 1995. This may have been attributed to a difference in the length of the hot period.
