Stenus pallipes Gravenhorst, 1802
Recorded throughout the Palaearctic region and widespread throughout Europe from the Pyrenees to the Balkans and north to the UK, Denmark and the Baltic countries, extending north into southern Sweden and Finland, this species tends to me more common in southern lowland regions and more scattered and local further north. In the UK it is locally common throughout England and Wales and much less so and more scattered further north as far as Inverness, it is present on some of the Western Isles but does not occur in Ireland. With the exception of peat bogs and other acidic situations the species is associated with a wide range of wetland habitats, it often occurs on well-vegetated margins of lakes, ponds and rivers or in marshes, fens and swamps etc but is also frequent by shaded pools in open woodland or in willow or poplar carr. Adults are present year-round; they overwinter among damp litter or among moss or tussocks and are active over a long season from February until late in the autumn, peaking in abundance from May until July, although individuals may be found during all but the coldest winter spells. They spend most of their time among litter or moss or on the surface among roots and vegetation but will climb stems during warm spells and now they sometimes occur in numbers on individual plants, they are may drop to the ground or onto water when disturbed and they can move rapidly across the water surface. The biology is unknown but they are probably typical of the genus with reproduction occurring in the spring and predatory larvae occurring in the same habitats as the adults. Adults are easily sampled by searching among or sweeping marginal vegetation, they also occur among suitable winter extraction samples and flood refuse.
3.5-4.0 mm. A small and rather parallel-sided species; body entirely black to very dark grey, usually shiny but sometimes appearing silky, palps entirely pale, antennae pale with the club darkened, legs entirely pale or with the femoral apices and tibial bases infuscated. Head distinctly broader than the pronotum, with a wide median ridge between large convex eyes, densely and moderately strongly punctured and with fairly dense white pubescence throughout. Neck wide and bulging, surface with distinct granular microsculpture. Pronotum slightly elongate, broadest at or slightly in front of the middle and narrowed to curved basal and apical margins, surface strongly and for the most part discretely punctured throughout, often smoothly convex but sometimes with an obscure median longitudinal impression. Elytra quadrate or nearly so and weakly dilated from sloping shoulders to recurved apical margins, surface slightly uneven and strongly punctured throughout. Abdomen long and gently tapering, three basal tergites strongly bordered, the others more weakly so, basal tergites strongly punctured throughout, the others more finely so. Legs long and slender, with tarsi distinctly shorter than the corresponding tibiae. Fourth tarsomere distinctly broader than the third tarsomere and bilobed, with the narrow lobes extending forward to beyond the basal third of the last segment.
From Tottenham, 1954