初冬期のダイズにおけるダイズサヤタマバエ（双し目：タマバエ科）の齢構成と生存率

Abstract

The soybean pod gall midge, Asphondylia sp., which is one of the serious pests of soybean in southwestern Japan repeats at least two generations from May to October on soybean and other wild leguminous plants. However the life history and host plants of the overwintering generation still remain unclear. The adults which emerged from soybean pods in October were considered to die without laying eggs, because no pods were available on any leguminous plants in late fall (OHSAKO et al., 1980). In this connection, the possibility that they might shift to alternate hosts other than Leguminosae was considered (YUKAWA et al., 1983) . To determine whether overwintering of this species occurs in Japan, soybeans were cultivated off-season, from September to December 1985, in exposing flowers and young pods to adults for oviposition from mid- to late October. The pod infestation rate was 10%, which is approximately normal for spring and summer. This means that the females normally searched for leguminous plants for oviposition even in October. Changes in the age structure indicated that the larvae developed in the fields, though slowly, into the pupal stage in December, which means their developmental zero point is relatively low. However all the pupae died in the pods withered by cold weather, while the emergence of an adult was observed under laboratory conditions. These observations on the developmental stages suggest that this gall midge does not enter diapause during the winter. Thus, such ecological attributes as searching behaviour for leguminous plants in late fall, low developmental zero point and non-diapause are considered to weaken the possibility that the gall midge overwinters in Japan either on Leguminosae or on other plant species.