Open Access

The North American species of the genus Eusphalerum Kraatz (Coleoptera, Staphylinidae, Omaliinae) are revised. The taxonomic history, natural history, geographical distribution of the genus, characters, species groups, diversity, and biogeography of North American species are presented. Two main phylogenetic lineages and 13 species groups are provisionally recognized. The following new synonymies are proposed: Eusphalerum farrarae (Hatch, 1944) = E. lawrencei Hatch, 1957; Eusphalerum californicum (Fauvel, 1878) = E. atriventre (Casey, 1894), = E. nigerrimum (Casey, 1894), = E. gilvipenne (Casey, 1894), = E. dichroum (Fall, 1922), = E. bonnelli (Hatch, 1944), = E. lunae Hatch, 1957; Eusphalerum fraternum (Casey, 1894) = E. minskae (Hatch, 1944); Eusphalerum rugulosum (Mäklin, 1853) = E. grayae (Hatch, 1944); Eusphalerum orientale (Bernhauer, 1912) = E. frosti (Bernhauer, 1928). The following lectotypes are designated: E. subangulatum (Casey), E. californicum (Fauvel), E. gilvipenne (Casey), E. diversicolle (Casey), E. convexum (Fauvel), E. fraternum (Casey), E. horni (Fauvel), E. orientale (Bernhauer), E. pothos (Mannerheim), and E. punctatum (Casey). The following new species are described: Eusphalerum pilosum (California); E. klimaszewskii (British Columbia); E. chatzimanolisi (California); E. carolinensis (Kentucky, Missouri, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia); E. caterinoi (California); E. luteipes (California); E. thayeranum (Alberta, British Columbia, Idaho, Indiana (doubtful record), Oregon, Washington); E. margaretae (Tennessee); E. newtoni (British Columbia, Oregon, California); E. parvispiculum (California, Oregon); E. uncinatum (British Columbia, California, Oregon, Washington). Eusphalerum lapponicum (Mannerheim, 1830) is excluded from the North American fauna. The following new combination is proposed: Xylodromus segmentarius (Mäklin, 1852: 322) (ex Omalium), wrongly attributed to Eusphalerum in the literature. Omalium marginatum Say, 1832 is considered a doubtful species, probably not Eusphalerum. A key to the 27 recognized North American Eusphalerum species and a catalog of the species are provided.