Geodromicus plagiatus (Fabricius, 1798)

Shavrin, Alexey V., 2022, The plagiatus species group of the genus Geodromicus Redtenbacher, 1857 (Insecta Coleoptera: Staphylinidae: Omaliinae), and additional data on some species from Japan, Zootaxa 5188 (5), pp. 401-429 : 403

Plagiatus group

Diagnosis. Body small to medium-sized (3.9–7.4 mm), with moderately small, slightly or distinctly transverse pronotum; aedeagus with narrow median lobe, gradually narrowed toward the subacute or rounded apex, parameres narrow or with very wide ( G. paramerus ) apical portions, internal sac with strongly sclerotized, wide, and moderately long flagellum.

Species included. G. plagiatus ( Fabricius, 1798) , G. corsicus Fagel, 1958 , G. magnus Shavrin, 2020 , G. nigrita (P.W.J. Müller, 1821) , G. paramerus Shavrin, 2000 , G. pedemontanus Fagel, 1958 , G. shii Cheng & Peng, 2020 , G. suturalis ( Lacordaire, 1835) .

Distribution. Species of the plagiatus group are distributed in the Palaearctic Region, from the British islands across Europe, Caucasus, Middle Asia to Siberia and central China. Additional species of this group can be found in North America, but the Nearctic species are in need of a comprehensive revision.

Bionomics. The species of the plagiatus group can be regarded as inhabitants of alluvial communities. The species inhabit gravel, stone, and sand-stone banks of streams and rivers; some East Palaearctic species were taken by sifting moss and litter near banks of streams and rivers ( G. paramerus , G. shii ). The species are represented from low to high elevations (70–4500 m a.s.l.). The beetles are usually collected from May to October. Bionomic data for G. magnus are unknown.

Remarks. Regarding the presence of a strongly sclerotized flagellum, the plagiatus group is somewhat similar to the Japanese aokii and sinuatus groups, from which it can be distinguished by the wider apical portions of the parameres. Additionally, it can be distinguished from the aokii group by the absence of two short parallel structures in the middle part of the median lobe, and from the sinuatus group by significantly narrower elytra and median lobe. I not provided here data on G. magnus , G. paramerus and G. shii in the species list below, because all labels data and figures of the habitus and the adeagus of these species can be found in Cheng et. al. (2020).