Xantholinus linearis (Olivier, 1795)
This is a widespread and generally common native Palaearctic species; it occurs throughout Europe to the far north of Fennoscandia, across North Africa including the Azores and Madeira, and east through Asia Minor and Russia to eastern Siberia. Following several introductions it is also established in the United States; from 1920 in the northwest and from 1976 in the northeast, and there are more recent records from Canada. Here it is generally abundant across England and Wales, including Anglesey and Man, and more local and sporadic further north to Shetland. Adults occur year-round in a wide range of mostly dry habitats although they may overwinter in damp moss on wetland margins, otherwise they are common in gardens and disturbed situations generally, on farmland where they may be significant predators of pests, grassland, woodland etc, they show no particular preference for soil type and are also common on dunes and beaches and regularly occur under patches of dry seaweed. Adults occur among decaying organic matter e.g. compost, leaf-litter, dung, fungi and carrion, they will often be found under logs and debris, especially in dry disturbed areas and during the warmest days of spring and summer may be found active on arable land or swept from long grass or in flight. Through the winter we have extracted them from moss and leaf-litter samples from a wide range of habitats, old avian nesting material from tree hollows and nest-boxes and they have been found at this time in mole nests. Sampling is straightforward as they will soon turn up when sweeping or sieving plant material, turning debris or pitfall trapping. This is our commonest member of the tribe.
Adults will need to be examined carefully in the field, especially when working dung, as there are several similar xantholinine staphs; they are obvious from the general habitus and all share the overlapping elytra but Xantholinus are distinct in having the posterior margin of the head rounded and the present species in particular in having strong linear microsculpture to the pronotum.
7-8mm. Head black, remainder of body variously dark to pale brown, often with the elytra contrastingly metallic reddish-brown. Head elongate with small, weakly-convex eyes and long temples, basal margin rounded and joining the neck at a distinct angle. Vertex and frons with fine linear microsculpture, extensively punctured and with long pale setae, clypeus deeply notched, mandibles produced forward sharply pointed apically and strongly toothed internally. Pronotum elongate and sub-parallel, anterior and posterior margins rounded, without distinct angles, surface each side of the centre with a longitudinal series of about 15 punctures, randomly and strongly punctured towards the lateral margins, entire surface with strong linear microsculpture. Elytra quadrate and widest at the rounded posterior angles, overlapping at the suture and truncate apically, surface diffusely and finely punctured. Abdomen long and parallel-sided, basal segments strongly bordered, apical segments less so, finely and quite densely punctured and pubescent and with strong transverse microsculpture.