動物学：偶然に発見されたハエに寄生する新種のハチ

A newly identified species of wasp that attacks and lays eggs inside an adult fly, rather than a larval stage, is reported in Nature this week. This is the first known case of a parasitoid wasp using adult fruit flies as hosts, despite fruit flies being an important model organism for scientific research. The discovery, which was made by chance during a screen of flies caught in backyards local to the researchers, highlights how undescribed biology can be found in highly studied organisms, demonstrating the value of ongoing insect research.

Parasitoids depend on host organisms for development; they lay their eggs in living creatures, which usually results in the death of the hosts as the adults emerge. Around 200 species of parasitoid wasps that target the fruit fly (Drosophila) have been discovered to date, all of which have been shown to target their hosts during vulnerable stages, such as when larvae or pupae. Until now, no wasp that attacks and develops inside the adult stage of a fruit fly host has been described.

Logan Moore and colleagues report the discovery of a new wasp species that infects the adult stage of the fruit fly. While monitoring nematode infections in wild fruit flies in backyards in Mississippi, USA in March 2023, the authors found a parasitoid wasp larva inside the abdomen of an adult male Drosophila affinis. They identify the wasp as a new species called Syntretus perlmani, from a subfamily of parasitoid wasps called Euphorinae that are known to infect adult insects, but not specifically Drosophila. Syntretus species have been known to occur in North America, but their hosts have remained elusive.

The serendipitous discovery enabled the authors to study the life history of this new parasitoid wasp, which may assist future research into parasite–host interactions.