Effect of predation by the specialist predator, Parena perforata Bates (Coleoptera: Carabidae) on population changes of the mulberry tiger moth, Thanatarctia imparilis Butler (Lepidoptera: Arctiidae).
Population changes of the arctiid Thanatarctia imparilis [Lemyra imparilis] and the carabid Parena perforata, a nest-inhabiting specialist predator of its larvae, were analysed in field studies conducted in Japan. The number of L. imparilis colonies decreased suddenly from 1989 to 1991 and gradually increased thereafter from 1991 to 1995. The carabid was observed in ca. 90% of prey colonies in 1990, but was not observed in 1991 and 1992. From 1993 to 1995, the density of P. perforata increased with an increase in density of L. imparilis. About 90% of L. imparilis larval colonies were destroyed before entering hibernation in 1990, while the destruction of larval colonies was only ca. 10% both in 1993 and 1994. Although predation by P. perforata acted strongly during periods of L. imparilis population decline, it did not act during periods of population increase. It is suggested that P. perforata is an important factor in regulating L. imparilis populations.