Establishment of Acanthoscelides pallidipennis (Coleoptera: Bruchidae) feeding in seeds of the introduced legume Amorpha fruticosa, with a new record of its Eupelmus parasitoid in Japan

A North American bruchid beetle Acanthoscelides pallidipennis (Motschulsky) was newly found on Kyushu Island, Japan, the larvae of which feed in seeds of introduced false indigo (or indigobush), Amorpha fruticosa L. (Fabaceae: Astragaleae). The morphological characters of the Japanese population were similar to those of introduced populations in Korea and China and of native populations in Texas. Plant quarantine records indicated that the introduction of A. pallidipennis was due to recent introductions of A. fruticosa seeds from China and/or Korea as soil cover on cut slopes. The proportions of seeds eaten by A. pallidipennis in three consecutive years (1997-1999) in Fukuoka, located in the northern part of Kyushu Island, were as high as 56.0% for the overwintered generation and 92.0% for the first generation feeding in the dry seeds of previous years. No parasitoid emergence was observed in the first two years. In 1999, however, Eupelmus sp. (Hymenoptera: Eupelmidae) had parasitized the overwintered generation at an extremely low level, which is the first record of a parasitoid of A. pallidipennis in Japan. Time lags required for parasitoids to use introduced phytophagous insects are reviewed. The ability of Eupelmus sp. and its host to overwinter and the short lag between our first observations of each of the two species in Japan may indicate a joint introduction of the parasitoid with its host.