Distribution and possible establishment of an invasive alien butterfly, the Red Ring Skirt (Hestina assimilis assimilis), in Yamanashi Prefecture

Abstract

An alien butterfly subspecies, Hestina assimilis assimilis, has been introduced to Kanagawa Prefecture and has been established there since 1998. This species is a potential competitor for two native butterflies, H. persimilis and Sasakia charonda. In the present study, we investigated the distribution and population density of H. a. assimilis larvae from Kanagawa Prefecture to the middle of Yamanashi Prefecture during the years 2012-2014, and examined the possibility that this species might overwinter in Yamanashi Prefecture. We found that the distribution of H. a. assimilis has extended to the middle of Yamanashi Prefecture. We also found that H. a. assimilis is physiologically able to overwinter in this area, but only with difficulty due to non-physiological factors. These results suggest that the alien butterfly H. a. assimilis is invasive in Yamanashi Prefecture and will compete with native butterflies if its population density increases in the near future.