Review of the genus Omalium Gravenhorst, 1802 (Coleoptera: Staphylinidae: Omaliinae: Omaliini) of Siberia and Far Eastern Russia, with notes on some species from Mongolia and Japan

A taxonomic and faunistic review of the genus Omalium Gravenhorst, 1802 of Siberia and Far Eastern Russia is presented, including notes on some species from Mongolia and Japan. Four species groups are established for 16 species of the genus: Amplissimum group containing O. longicorne Luze, 1906 (Mongolia, eastern Siberia); Caesum group containing the Palaearctic O. caesum Gravenhorst, 1806 and O. golovatchi sp. nov. (Russia: Kemerovo Area); Oxyacanthae group containing the Holarctic O. oxyacanthae Gravenhorst, 1806 and Palaearctic O. septentrionis Thomson, 1857; Rivulare group containing the Palaearctic O. curtipenne Mklin, 1878, Japanese O. diffine Sharp, 1889, O. hibernum Hayashi, 2006, as well as O. shibatai Watanabe, 1990 and O. kurilicum sp. nov. (Russia: Kuril islands: Iturup, Kunashir), O. japonicum Sharp, 1874 (Japan, South Korea), O. niponense Sharp, 1889 (Far Eastern Russia, Japan), Holarctic O. rivulare (Paykull, 1789) and O. strigicolle Wankowicz, 1869, Mongolian O. scabrum Smetana, 1975, and O. subsolanum Herman, 2001 (Siberia, Japan); and unspecified group containing the Japanese O. tenue Weise, 1877. All new species, and O. curtipenne, O. diffine, O. longicorne, O. niponense and O. subsolanum are (re-)described and illustrated. A new synonymy is established: O. curtipenne = O. lacki Bernhauer, 1940 syn. nov. Lectotypes are designated for O. clavatum Luze, 1906, O. japonicum and O. lacki. The habitus of O. oxyacanthae, O. scabrum and O. septentrionis, and, in addition, the aedeagus and female accessory sclerites for O. japonicum and O. strigicolle are illustrated. A checklist and key to all species of Omalium of Asian part of Russia eastwards of Ural Mts., Mongolia and Japan are provided. Three species, that were based on the misidentifications, are excluded from the fauna of Siberia: O. allardii Fairmaire & Brisout, 1859, O. excavatum Stephens, 1834 and O. foraminosum Mklin, 1852. Distributional maps for the new species and O. curtipenne, O. diffine, O. longicorne, O. niponense and O. subsolanum are given. Several species of Omalium are recorded from a certain area for the first time: O. curtipenne from Tyumen Area, Evenkia, Chita Area, Yakutia, Magadan and Amur areas, O. longicorne and O. oxyacanthae from Amur Area, O. niponense from Russia (Maritime Province), O. rivulare from Khanti-Mansi Autonomous region, Tomsk and Novosibirsk areas, O. septentrionis from Khanty-Mansi and Taimyr autonomous regions, Evenkia, Tuva, Amur Area and Khabarovsk Territory, O. strigicolle from Khanty-Mansi Autonomous Region, Tyumen Area, Krasnoyarsk Territory, Evenkia, Tuva, Amur Area and Khabarovsk Territory, and O. subsolanum from Amur Area and Japan.