Morphology and biology of a phytophagous ladybird beetle, Epilachna pusillanima (Coleoptera: Coccinellidae) newly recorded on Ishigaki Island, the Ryukyus

Abstract

The occurrence of Epilachna pusillanima was confirmed on Ishigaki Island, the Ryukyus, southernmost Japan, in June, 1997. This is the first record of the species from Japan. E. pusillanima infested two cucurbitaceous weeds, Trichosanthes bracteata and Trichosanthes sp. 1, but was not observed on cucurbitaceous crops, though it is known as a notorious pest of cucurbits in Southeast Asia. E. pusillanima is externally similar to another cucurbit feeder, E. boisduvali, which also occurs on Ishigaki Island, in that both have 12 spots on the elytra and similar body size. However, the two species are easily distinguished by 1) the structure of the genitalia of both sexes, 2) the color and maculation of prepupae and pupae, and 3) diet. Results of a mate choice experiment suggest that E. pusillanima and E. boisduvali are reproductively isolated by ethological isolation and/or gametic isolation.