Potential distribution area of the Mexican bean beetle, Epilachna varivestis (Coleoptera: Coccinellidae) in Japan, estimated from its high-temperature tolerance.

Abstract

Thermal responses in regard to female oviposition and larval development were investigated in the invasion population of the Mexican bean beetle, Epilachna varivestis whose presence was initially confirmed in Yamanashi and Nagano Prefectures, central Japan in 1997. Oogenesis in the female was inhibited when exposed to 27.5°C for five continuous days. Larval development was inhibited markedly at 30°C, and survival rate declined to nearly 0% when exposed to 32. 5°C for more than five days. Based on these high-temperature stresses and the 30-year average temperature data in Japan (1961-1990), we estimated the potential distribution area of E. varivestis in Japan. It is predicted that E. varivestis will be less abundant in the south-western areas of central Japan, while this beetle could survive efficiently and maintain a high population level in the mountainous areas of central Japan, and in almost all of northern Japan (Tohoku and Hokkaido).