A review of Canadian and Alaskan species of the genera Clusiota Casey and Atheta Thomson, subgenus Microdota Mulsant & Rey (Coleoptera, Staphylinidae, Aleocharinae).

This paper treats 13 species of the subgenus Microdota Mulsant & Rey of Atheta Thomson and 3 species of the genus Clusiota Casey in Canada and Alaska. We report here 4 species new to science, and 3 new provincial records. The following species are new to science: Atheta (Microdota) curtipenis Klimaszewski & Webster, sp. n., Atheta (Microdota) formicaensis Klimaszewski & Webster, sp. n., Atheta (Microdota) macesi Klimaszewski & Webster, sp. n., and Clusiota grandipenis Klimaszewski & Webster, sp. n. The new provincial records are: Atheta (Microdota) pseudosubtilis Klimaszewski & Langor, new to AB, and Atheta (Microdota) subtilis (Scriba), an adventive Palaearctic species new to North America, first reported in LB and NB. The two Clusiota Casey species are reviewed, and their distribution is revised. A female Clusiota impressicollis was discovered in Ontario and is illustrated here for the first time. A key to all Canadian species of the subgenus Microdota and genus Clusiota are provided. Atheta (Microdota) holmbergi Bernhauer and Atheta (Microdota) alesi Klimaszewski & Brunke are transferred here to the subgenus Dimetrota Mulsant & Rey.