Dyschirius globosus (Herbst, 1784)
Often quoted as a subgenus of Dyschirius Bonelli, 1810, Eudyschirius Federenko, 1996 is now generally classified as a subgenus of Dyschiriodes Jeannel, 1941 (itself formerly a subgenus of Dyschirius), and includes 12 European species of which globosus is the only one to occur in the UK. This species is generally common from lowlands to low mountain altitudes throughout the Palaearctic region from Portugal to the far east of Russia, extending south to Algeria and Morocco and north to the UK and the far north of Fennoscandia, it has also become established in the west of Canada and the north-western United States, having been first recorded in the 1970s. Here it is common and often abundant throughout the UK including all the islands north to Shetland. Typical habitats include most wetland marginal areas; adults are usually encountered on open or sparsely vegetated areas of permanently damp muddy or silty soil, sometimes far from water, but they are fairly eurytopic, occurring on peaty and sandy substrates, including coastal saline pools, dunes and seashores, damp pasture and upland bogs etc. and they occasionally occur on dry areas of heather moorland. Adults are predatory, they are not associated with Bledius (Oxytelinae) but have been observed predating Carpelimus (Oxytelinae), they occur year-round and are active over a long season, from February or March until October or November depending on the season in early spring. Reproduction occurs in spring or early summer with new-generation adults appearing in late summer and autumn and overwintering. Adults appear to be consistently short-winged although fully-winged specimens are known from the continent. They may be sampled by pitfall trapping or grubbing among marginal vegetation, flooding areas of bare marginal substrate may produce them in numbers and they occasionally occur in flood refuse or among extraction samples from marginal situations through the winter.
Measuring 2.3-2.9mm this is the smallest of our scaritine fauna and this small size is usually sufficient to identify the species. Adults are distinctive; very convex with the margins of the pronotum and elytra strongly rounded, body entirely shiny black with a weak metallic reflection, appendages pale to dark brown. Head smoothly convex between large and convex eyes, mandibles robust and produced forward, antennae moderately long; usually dark with 1-3 basal segments extensively pale. Pronotum weakly transverse, with a variously developed median longitudinal impression but otherwise smoothly convex, lateral margins almost smoothly rounded and bordered only in the anterior half; the border not extending to the posterior setiferous puncture. Elytra relatively short, about 1.6X longer than wide, lacking a basal border and with strongly punctured striae that fade laterally and apically, being usually faint or absent from the apical third, with three sub-humeral foveae, three humeral and three subapical punctures, the lateral margins otherwise impunctate. Front tibia with a small sharp tooth on the external margin near the base of the produced apical tooth, middle and hind tibiae without external teeth.