A host shift from wild blue cohosh to cultivated potato by the phytophagous ladybird beetle, Epilachna yasutomii (Coleoptera, Coccinellidae)

摘要

Life history traits of the phytophagous ladybird beetle Epilachna yasutomii were compared between a nonpest population feeding on wild blue cohosh (Caulophyllum robustum) and a pest population feeding on cultivated solanaceous crops, mainly potato (Solanum tuberosum) in Nagano Prefecture, Japan. Newly-emerged adults of the nonpest population entered diapause early in midsummer when blue cohosh withered, while adults of the pest population were found in tomato and eggplant [aubergine] fields until late autumn. The pest population had larger females, a higher population growth rate, a shorter larval development period, and reduced longevity of overwintered females, compared with the nonpest population. ANOVA indicated that all these life history traits were influenced by the food plant, and that the number of eggs oviposited per female and the longevity of overwintered females were also affected by the population type. These findings suggest that the life history pattern of E. yasutomii changed tohigh fecundity with a short life span from low fecundity with a long life span as a result of the host shift from wild blue cohosh to cultivated solanaceous crops.