Tasgius melanarius (Heer, 1839)
This widespread and generally common species occurs throughout central Europe reaching Italy and Albania to the south and the southern provinces of Fennoscandia and the UK to the north, further east it extends through the Caucasus, Turkey and much of Russia. First recorded in the Nearctic region in 1935 from Quebec the species is now established and widespread in the northern United States and parts of southern Canada. In the UK it is generally common through England and Wales, with the probable exception of the West Country, and more local and scarce further north to the Scottish Highlands. Adults occur year-round; appearing early in the spring and peaking in abundance during May and September; they are mostly nocturnal and spend the day under logs and debris. They occur in a wide variety of dry or moderately damp habitats including coastal dunes and beaches, woodland, arable land, parkland and waste-ground and they are common in gardens and other regularly-disturbed areas, sometimes entering houses at night. They will often be seen at night walking on pathways and lawns or climbing low down on tree trunks, especially towards the end of summer when they seek sites to overwinter, they are predatory and we have seen them feeding on dead insects, snails and slugs on pathways in local parks. They may be found under logs and among leaf-litter etc, especially on grassland, among compost and will regularly occur in pitfall-traps, little is written about the life-cycle and we have observed them mating on only one occasion; during June in a local woodland.
With the exception of Ocypus olens, this is our commonest large staphylinid and it will soon become familiar from the form of the pronotum but there are several similar large species and so initially specimens should be examined critically.
14-17mm. Entirely dull black with a faint blue reflection to the head and pronotum or sometimes with the elytra dark reddish-brown. Head transverse and at least as wide as the pronotum, with small eyes continuous with the outline and relatively long, rounded temples, vertex very finely punctured between the larger punctures. Antennae dark or paler towards the apex; the second segment sometimes paler but dark at the base, palps pale. Mandibles long and tapering to a blunt apex, without internal teeth and more-or-less straight along the middle of the inner margin; in some similar species this margin is sinuate. Pronotum quadrate and distinctly narrowed from rounded anterior angles to the curved basal margin, surface densely and quite strongly punctured, the punctures subequal in size, with a smooth longitudinal area which is broadest at the base and often obliterated towards the apex. Scutellum large and triangular; strongly microsculptured at the base and becoming smooth towards the apex. Elytra quadrate to slightly transverse, with sloping shoulders and curved laterally, widest behind the middle and truncate apically, surface evenly and densely punctured giving a smooth matt appearance. Abdomen proportionally very long; tergites finely and quite densely punctured, microsculpture stronger towards the base and apex of each. Legs black or with the tarsi pale.