Bembidion tetracolum Say, 1825
A widespread and generally common native species throughout Europe, Asia Minor and east through Siberia; it was first recorded in America in 1823 and is now widespread across the northern Nearctic region. It occurs commonly throughout the U.K. including the Western Isles and Orkney. Adults are present year- round; they breed and disperse in the spring and are nocturnal as well as diurnal predators. They occur in a wide range of habitats; wetland margins, dunes and seashores as well as grassland and arable land where they are considered beneficial as they consume large numbers of insect eggs. In general they occur in open and damp situations with scattered vegetation, or under debris or logs etc in shaded sites where they may be active throughout the year. This is one of the commonest U.K. Bembidion species and is usually found in numbers and often among populations of other carabids; they often occur among flood refuse, reed litter and in grass tussock samples during the winter.
This is a member of the subgenus Peryphus Dejean, 1821, a group of about 125 mostly Palaearctic species (depending upon how it is defined) of which 13 occur in the U.K. Although distinctive there are several closely similar species, see below.
4.9-6.1mm A convex species with the head and pronotum shiny black, green or, rarely, blue and the elytra dark with humeral and sub-basal pale macula separated by the ground colour to the lateral margins; in B. maritimum (Stephens, 1835) they are continuous laterally. The head is smooth but for the supra-orbital punctures and the shallow, almost parallel, furrows which do not continue onto the clypeus. The legs and palps are entirely pale and the antennae are dark with 3 pale basal segments; in the similar B. bruxellense Wesmael, 1835 the third antennal segment and the femoral bases are dark. Pronotum cordiform with wide basal fovea and without microsculpture on the disc; the hind angles are sharp and the lateral bead is visible from above throughout. The base extensively punctured, usually confluently around the middle. Elytral intervals convex and dull due to transverse microsculpture (X50), the setiferous punctures join the third stria and the basal stria is rounded below the humerus. All dorsal striae punctured and well impressed to the middle, becoming weaker toward the apex; the seventh evident to at least the middle and the eighth deeply impressed and joining the marginal stria in the basal third. Apterous, or with rudimentary wings. Male pro-tarsal segments dilated.