Revision of the intertidal rove beetle genus Bryothinusa from Japan (Coleoptera: Staphylinidae: Aleocharinae)

The Japanese species of the intertidal rove beetle genus Bryothinusa Casey, 1904 are revised. Of 17 recognized species in total, six known species (B. algarum Sawada, 1971, B. gangjinensis Ahn & Jeon, 2004, B. minuta (Sawada, 1955), B. nakanei (Sawada, 1955), B. sakishimana Sawada, 1991, B. tsutsuii (Sawada, 1955)) are redescribed and nine new species (B. aikoae sp. nov. from Honshu, B. constricta sp. nov. from Honshu, B. fulvipennis sp. nov. from Honshu and Shikoku, B. hokkaidensis sp. nov. from Hokkaido and Kyushu, B. itsuroi sp. nov. from Honshu, Kyushu and Nansei-shoto, B. moriguchii sp. nov. from Nansei-shoto, B. nigra sp. nov. from Honshu, Shikoku, Kyushu and Nansei-shoto, B. okinawana sp. nov. from Nansei-shoto, B. yoshigoui sp. nov. from Honshu) are described. Additional descriptions and records for the two species (B. koreana Ahn & Jeon, 2004 and B. japonica Liu, Ono & Maruyama, 2020) which are currently described/redescribed are given. Mouthparts and sexual organs of both sexes of all species are illustrated. A key to the Japanese species and distribution map of these species are provided. The habitats and behaviour of some representatives are reported, and the distributional range related to flight ability is discussed.