The matatabi fruit gall midge, Pseudasphondylia matatabi, is known to cause fruit galls on Actinidia polygama (Actinidiaceae). The galled fruits are flattened and divided into several parts with longitudinal furrows while the normal ones are oval and have a smooth surface. The midge larvae mature in autumn and pupate in the galls. The adults emerge in October to November a little before or soon after the galls start to drop to the ground. Since many (up to 50) midge larvae inhabit a gall, it is difficult to know the density of the midge population in the field by counting the number of galled fruits. Therefore, this study is intended to find a practical way to estimate the number of midge larvae in a gall without dissection. We examined the relationship between the number of midge larvae per gall and the diameter, height, volume (diameter x height) or weight of galled fruits. The galls were collected from Kagoshima and Miyazaki Pre-fectures in 1969-1992. The results of the examinations indicated that the number of midge larvae per gall was estimated by measuring the diameter (r = 0. 778) when the galls were not attacked by the larvae of Hydrillodes lentalis (Lepidoptera: Noctuidae). When the galled fruits are attacked by the lepidopterous larvae, there was no high correlation between the number of midge larvae and the gall size, but the former was esti-mated well by weighing the galls (r=0.875).
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