Philonthus cognatus Stephens, 1832
This species is generally common from lowlands to low mountain altitudes throughout the northern Palaearctic region, in Europe it is present from the Mediterranean to beyond the Arctic Circle in Fennoscandia and in many countries is the most common member of the genus, it is widespread across North Africa and the Near East and recently been recorded from The Middle East, it has also become widely established in North America following accidental introductions in the ninetieth century. In the UK it is common and often abundant throughout England and Wales including the islands, and sporadic and local further north to the Scottish highlands, Hebrides and across Northern Ireland. Adults occur year-round and peak in abundance during the spring and again in September and October when the new generation emerge, they are associated with decaying organic matter in a wide range of damp, or at least not too dry, habitats, often in woodland and on dung pasture but also in disturbed habitats such as domestic gardens, parks and arable land. Adults are predatory and mostly nocturnal but they fly well and often do so on warm sunny days, often alighting on vegetation of landing on pathways and running rapidly, at night they roam pathways and short turf and sometimes climb trunks and walls in search of prey which consists of small insects etc, and among arable crops they are considered to be beneficial as they consume large numbers of aphids. Breeding occurs in spring and early summer and the predatory larvae develop through the summer, hunting in much the same habitats as the adults, they pupate in the ground later in the summer and adults emerge from August or September. Adults are easily found by searching at night, they may be common among decaying leaf-litter and dung and sometimes occur at carrion, later in the year they may be abundant among decaying fungi, and through the winter may be found under logs and debris and are common in tussocks and among suitable extraction samples. Because they are active on warm sunny days they often appear when sweeping dense vegetation, often from nettle-beds and occasionally from umbel flowers, they run very rapidly and quickly take flight and so may be difficult to capture, and for the beginner are likely to be among the first members of the genus to be encountered.
Philonthus cognatus 1
Philonthus cognatus 2
Philonthus cognatus 3
8-11mm. Among the easiest of our Philonthus species to identify; the size, bicoloured basal antennal segment and arrangement of pronotal punctures is diagnostic. Head and pronotum shiny black with a (sometimes weak) greenish or bronze metallic reflection and distinct microsculpture, elytra black with a metallic reflection which may be the same as the forebody or may contrast in intensity or colour, abdomen black with a different metallic reflection, often bluish, appendages black but the basal antennal segment is yellow below. Head narrow and slightly elongate, temples sloping and about the same length as the eyes, eyes continuous with the outline of the head and occupying slightly more than half the lateral margin. All segments of the antennae and palps elongate. Pronotum quadrate, rounded posteriorly and laterally to distinct anterior margins, surface with distinct wavy transverse microsculpture and a series of four strong punctures either side of the disc as well as others towards the margins. Elytra quadrate or slightly transverse, with sloping shoulders and only weakly dilated to rounded posterior margins, the surface densely punctured and finely pubescent, the punctures often appearing to from transverse rows. Abdomen smooth and shiny, densely punctured but without microsculpture, and with long dark pubescence. Males may be distinguished by the more strongly dilated front tarsi.