Taxonomic revision of the extant species of the Japanese Stephanidae (Hymenoptera), with discussion on distribution pattern and conservation importance

The Japanese species of the family Stephanidae Leach, 1815 are revised. A total of nine extant species are recognized from Japan, including two new species, Megischus pretiosus sp. nov. and Parastephanellus ryukyuensis sp. nov., and one species, Foenatopus ruficollis (Enderlein, 1913), is newly recorded from Japan. The female of Foenatopus cervinus Townes, 1958 and the male of Megischus baogong Ge & Tan, 2022 are newly described. A key to the Japanese genera and species of this family is proposed. The biogeographic pattern and the origin of Japanese stephanids, the role of Kuroshio Current, and the conservation importance of endemic species to the Ogasawara (Bonin) Islands are also discussed.