Bembidion articulatum (Panzer, 1796)
This transpalaearctic species is generally common throughout lowland Europe to about 1000m except for some extreme southern and northern parts, and in many countries is among the most common of the wetland members of the genus, it is continuously distributed from Portugal and the UK in the west to China and Japan in the east, it is also common through Asia Minor and on many Mediterranean islands but is absent from North Africa. In the UK it is generally common across lowland England north to Yorkshire and there are a few records from Wales, Anglesey and the west of Scotland but it is otherwise absent further north and from Ireland. Adults are present year-round, peaking in May and June and decreasing in numbers through the summer although there is often a smaller peak later in the summer or into the autumn, they are mainly diurnal but will also be found active at night, typical habitats include exposed and poorly-vegetated freshwater margins on clay or silty soil, they are common at moorland ponds and peat bogs and often occur among gravelly or loamy substrates but generally avoid pure sand. During the autumn they migrate away from marginal areas to overwinter in dry or damp soils or under debris, in general they do not move very far even though they are good fliers, and they probably go deep into the soil as they are rarely recorded at this time. They appear at marginal habitats early in the year and are generally active in numbers from March, breeding begins in the spring and continues into the summer and teneral adults appear from late August, the life history is unknown but both adults and (probably) larvae are predatory, as is usual for the genus. Adults can hardly be missed as they run in bright sun but they quickly vanish into cracks in the soil or under debris when disturbed, due to their distinctive colouration they soon become obvious in the field and in most cases they will be found to occur among numbers of other marginal Bembidion species and so some time should be spent looking carefully at specimens. Pitfall trapping is a very effective way of sampling adults but can be very destructive, an equally good and much kinder method is to flood small areas of substrate and wait for the beetles to emerge from the soil, this will be found to produce a large variety of carabids as well as other beetles.
Bembidion articulatum 1
Bembidion articulatum 2
Bembidion articulatum 3
Bembidion articulatum 4
2.9-4.0 mm. Very typical of the genus with a wide head, narrow pronotum and broadly-oval elytra, head and pronotum shiny black with a metallic green or blue reflection, elytra very variable but always with the base, including the shoulders, substantially pale, otherwise with variously developed dark transverse bands or spots, legs pale brown, antennae dark with up to four basal segments pale. Head with large convex eyes and short converging temples, inner margin of the eyes with two setiferous punctures, vertex smoothly convex and at most with sparse punctures behind the eyes, frontal furrows deeply impressed and strongly converging anteriorly, almost joining on the clypeus. Antenna long and filiform, terminal maxillary palpomere diminutive. Pronotum broadest in front of the middle and sinuate in front of almost perpendicular posterior angles, surface smoothly convex, basal margin with four small depressions between the larger fovea inside the angles. Elytra with seven strongly punctured striae which fade behind the middle, the third with two setiferous punctures, basal border smoothly curved under the shoulders. Legs long and slender, pale brown or with the femoral apices darkened, basal pro-tarsal segments dilated in the male.