Bembidion dentellum (Thunberg, 1787)
This is the only U.K. member of the subgenus Eupetedromus Netolitzky, 1911, a small group of about 10 Palaearctic species. It is a widespread and generally common Palaearctic species extending to eastern Siberia and north to Sweden and Finland. Adults become active during the first warm days of spring and are soon common, remaining so until the autumn. Typical habitats are marginal and wetland situations; pond and river margins, seepages and fluctuating marshes etc. and are characteristic of river sediment carabid populations. They occur in a wide range of damp situations, and searching lightly vegetated silty or sandy areas, especially in sunny conditions when they are active, is a good way to record them. During overcast conditions they generally hide beneath stones etc. or among dense vegetation, and in the summer when the ground dries out they rest in cracks in the substrate where it remains damp. Adults are diurnal predators and can run rapidly in search of prey; in sunlight the cryptic nature of the dorsal surface becomes apparent and they can be difficult to follow. During the winter they remain under debris or among tussocks etc., often some distance from water, and turn up regularly in flood refuse. They are quick to colonize new habitats and generally occur among populations of other wetland carabids.
This relatively large Bembidion soon becomes obvious in the field. 5-6mm. The head and pronotum are dark metallic bronze, the elytra dark with a pattern of transverse fascia fenestrated by the dark striae towards the apex. Head relatively large and with dense microsculpture; the anterior setiferous puncture inside a raised shiny area at the base of each deep frontal furrow. The furrows converge on the clypeus and do not reach the labrum. Antennae and palps dark with the base pale. Pronotum transverse and cordate; curved and strongly margined laterally, with broad and punctured basal foveae and a fine ridge between these and the lateral margin. The basal margin is almost straight and the lateral margins have two long setae; one at the hind angles and one near the centre. Elytra iridescent due to transverse microsculpture, basal margin curved parallel to the shoulders and the third interstice has two setiferous punctures which do not touch the striae. All striae punctured in the basal half and distinct to the apex. Legs brown with the femora to some extent metallic. Male with two basal tarsal segments dilated.