Reproductive ethology of the Fijian predator-inquiline wasp Pseudofoenus extraneus (Hymenoptera: Gasteruptiidae: Hyptiogastrinae).
Parasitoid wasps of the subfamily Hyptiogastrinae (Gasteruptiidae) are known to lay eggs in the nests of solitary bees and wasps. Their larvae are considered predator-inquilines, consuming the host's eggs and larvae and then the nest provisions. Pseudofoenus extraneus is endemic to Fiji, and the only member of the subfamily Hyptiogastrinae known to have colonised the archipelago. The host relationships and oviposition sequence of this species have not been previously reported. We show that the primary host is the halictine bee Homalictus fijiensis and describe P. extraneus behaviour around Homalictus nest aggregations and the entering of host nests. Wasps were observed entering Homalictus nests on nine occasions, as well as perching near nests and antennating nest entrances. The high abundance of H. fijiensis in Fiji may help to explain how a parasitoid was able to successfully invade such a remote oceanic archipelago as Fiji.