Stenus flavipes Stephens, 1833
This widespread species occurs throughout Europe from the Mediterranean north to central Sweden and the UK, to the south it extends to northwest Africa and to the east into Siberia, through much of this range it is locally common in wetland situations but in northern regions it can be sporadic e.g. it is very local and rare in Poland while it is generally common throughout Denmark. In some Mediterranean regions such as Italy, Portugal, Spain and Morocco it is also represented by S. flavipes dobberti Quedenfeldt, 1882, which has longer elytra and fully-developed wings. Here it is generally common throughout Wales and south and central England, including all the islands, and more local and rare north to southern Scotland. Typical habitats include a variety of well-vegetated wetland situations, wet meadows, marshes, pond and river margins, reed beds, carr and peatland pools where the adults may be found active on the soil surface or among moss and litter, and during warm weather they also climb plant stems in search of prey and are easily observed Adults are present year-round, they overwinter among litter or in hollow stems and will soon occur among extraction samples from marginal situations that are not prone to flooding, they become active in April or May and are soon common among the many other rove beetles present in such situations, they will occur in pitfall traps but during warm weather may be swept from dense marginal vegetation or reed bed margins in numbers.
This small, slender and rather parallel-sided species is easily identified by the colouration and the form of the tarsi. Body entirely shiny or silky black, sometimes faintly metallic, with scattered white recumbent pubescence, legs and palps pale yellow, antennae yellow with the basal segment and two apical segments dark. 3.4mm. Head much wider than the pronotum and slightly wider than the elytra, strongly and quite densely punctured throughout and broadly impressed beside the eyes, the vertex longitudinally convex. Pronotum elongate and broadest about the middle, lateral margins rounded to distinct anterior angles and slightly constricted before posterior angles, basal and apical margins almost straight, punctation strong but not dense or confluent. Elytra elongate with sloping shoulders and weakly dilated to the apex, punctures about as strong as those on the pronotum but often a little denser. Abdomen with distinctly raised lateral borders, at least to the first four tergites, all segments moderately strongly and densely punctured. Legs entirely pale yellow or with, at most, the tips of the femora darkened. All tarsi broad and much shorter than the hind tibia, each with the second and third segments expanded, the third slightly wider than the second, and the fourth segment strongly bilobed, the lobes extending more than half the length of the terminal segment. Claws and extreme tip of the terminal tarsomere dark.