Xantholinus tricolor (Fabricius, 1787)
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POLYPHAGA Emery, 1886
STAPHYLINOIDEA Latreille, 1802
XANTHOLININI Erichson, 1839
Xantholinus Dejean, 1821
This species occurs throughout much of the northern Palaearctic region from Europe to and Asia Minor to the far east of Russia, in Europe it occurs from the Pyrenees to northern Italy, the Balkan Peninsula and Ukraine in the south and north to the UK, Denmark and above the Arctic Circle in Fennoscandia. Throughout most of central and northern Europe it is generally common and occurs from lowlands to the Alpine zone whereas in the south it is more frequent in upland situations. In the UK it is very local and rare; there are scattered records from Central England and it occurs in the Scottish Highlands where it is probably widespread, it has probably declined over the 20th century as Fowler quotes it as occurring across the south, both inland and in coastal situations, and as being not uncommon in the London district. On the continent it is rather eurytopic, occurring on waste ground and disturbed sites such as road verges and parkland etc but in the north it occurs mostly in woodlands, and especially coniferous woodlands, while at higher altitudes (up to 2700 m in the Alps) it occurs among decaying vegetation and under debris in wet situations. The typical UK habitat is unknown but Fowler records it from vegetable refuse and decaying seaweed. In woodlands the species may be found among leaf-litter, tussocks and moss or under dead bark and adults have been recorded from flight-interception traps placed in trees. Adults have been recorded from March to December, peaking in abundance during May and June. The biology is unknown but adults probably overwinter, as is typical of the genus, and reproduction probably occurs in spring and early summer with the new generation appearing in late summer and autumn.
9-10 mm. Elongate and rather parallel-sided with a large head which is wider than the pronotum and the elytra across the shoulders, head black or dark grey, pronotum reddish with ill-defined dark areas towards the base, scutellum and elytra pale brown, abdomen dark reddish-brown with paler margins to the tergites and the apical tergites more extensively pale; in lighter specimens the fifth visible tergite is darkened only across the base and the sixth is more or less completely pale, but in any case the sixth is always broadly pale across the base, antennae dark reddish-brown, legs paler brown. Head convex and elongate, broadest before a smoothly rounded base and narrowed to projecting mandibles, eyes small and more or less continuous with the outline, surface convex with scattered large punctures and an oblique impression extending from the anterior margin of each eye onto the clypeus, mostly smooth, with cellular microsculpture only towards the margins. Antennae inserted dorsally inside the outer margin of the mandibles, only slightly longer than the head and separated by less than the length of the basal segment, segments 2 and 3 elongate, 4-10 transverse and the terminal segment elongate and pointed. Neck transverse, bulbous and finely punctured across the anterior quarter. Pronotum elongate, broadest before a rounded anterior margin and narrowed to curved posterior angles and basal margin, lateral border reflexed down towards the front, surface smooth, without microsculpture, with scattered large punctures outside a longitudinal series of 11 or 12 punctured either side of the disc. Scutellum large, triangular and bisinuate across the base. Elytra slightly dilated from rounded shoulders to reflexed apical margins, suture overlapping, surface with random large punctures and sparse fine golden pubescence. Abdomen strongly bordered, all tergites with strong cellular microsculpture, very fine punctures and sparse pale pubescence. Femora long and robust, tibiae broadened from the base, with strong spines along the external margins and a long terminal spur. All tarsi with five simple segments.