Polymodal emergence pattern and parasitoid composition of Asteralobia sasakii (Monzen) (Diptera: Cecidomyiidae) on Ilex crenata and I. integra (Aquifoliaceae)

Abstract

In a population of the gall midge Asteralobia sasakii, we discovered individuals that entered a prolonged diapause. To interpret the adaptive significance of this prolonged diapause, the life history of A. sasakii was investigated in relation to parasitoid attacks. The survey was conducted on two host plants, Ilex crenata and I. integra in central Honshu, Japan. The majority of midges were univoltine and spent only one winter as mature larvae. On I. integra, some individuals diapaused in the first stadium and spent two or more winters, so that the total emergence pattern was a polymodal pattern. The advantage of the prolonged diapause was unclear. Allochronic isolation was found between the two host-associated populations of A. sasakii in the field. The two populations of midges also differed in the species composition of parasitoids. Our results suggest that the two populations of A. sasakii belong to two distinct biological species.