Life Tables of the Migrant Skipper, Parnara guttata guttata BREMER et GREY(Lepidoptera:Hesperiidae)in the Northern Peripheral Area of Its Distribution

Abstract

Life table studies in the immature stages of Parnara guttata guttata BREMER et GREY were conducted in the northern peripheral area of its distribution, Joetsu, Niigata, Japan. The mortality by parasitoids in the 4th and 5th instar larvae and pupae was high. Egg parasitism rate was low. Fifteen primary and seven secondary parasitoids were recorded. Among them, four primary and four secondary parasitoids were newly recorded from P. g. guttata. A host-specific parasitoid, Apanteles baoris WILKINSON and an oligophagous parasitoid, Pediobius mitsukurii (ASHMEAD) were predominant even in Joetsu where the hibernation of the host species is impossible. In addition, two subsidiary mortality factors were detected: 1) predation of the 5th instar larvae and pupae by large predators (mainly birds) in the 1st generation, and 2) failure in settlement of hatchlings on leaves in the 2nd generation. The latter was more important on the normal planting rice than on late planting rice. these results were compared to those in central and western Japan where P. g. guttata can hibernate.