Dispersion of a Torymus (Syntomaspis) sinensis population in Fukuoka Prefecture (Hymenoptera: Torymidae)

Abstract

A small scale release of an imported parasitoid, Torymus (Syntomaspis) sinensis KAMI-JO was attempted at Mt. Aburayama, Fukuoka in 1981, but the parasitoid was not recovered until 1990. In order to determine the dispersion and growth of the parasitoid population in Fukuoka Prefecture, galls of the host cynipid were collected from sixteen sites from November 1990 to March 1991. T. (S.) sinensis adults emerged from galls collected at nine sites from every direction of the release point, even at a point as far as 19 km to the northeast. The maximum number of T. (S.) sinensis females per 100 galls was 26. 9 at a site close to the release point. Facultative hyperparasitoids may possibly affect adversely the growth of the introduced parasitoid population.