Psammoecus bipunctatus (Fabricius, 1792)
This is the only British member of a large genus of about eighty species of small silvanids to occur in mainland Europe although another species, P. personatus Grouvelle, 1919 (distinct in having strongly denticulate pronotal margins) is present on Madeira. The genus has an almost cosmopolitan distribution but is by far most diverse in Old World tropical regions and only poorly represented in temperate areas and the New World generally. The present species is locally common through much of Europe, being absent from some south-eastern regions, extending north to the UK and southern Sweden and east into Russia, here it is common across South Wales and England north to Yorkshire although absent from the West Country and (probably) the Isle of Weight. This is a strictly wetland species, occurring on permanently wet river and lake margins, marshes, fens and, especially, in reedbeds. Adults generally occur among accumulated plant litter but in warm weather they climb stems and may form flying swarms in the evening, they usually occur in large numbers and may occasionally be found away from water as they disperse. Little is known of the biology but adults occur year-round, they overwinter in stems of reeds and rushes or among bundles of fallen stems, and become active from April, numbers peak in late spring and again in late summer when teneral specimens are present and it is thought that larvae develop through the summer among plant litter. Adults are readily sampled by sweeping wetland habitats in warm weather.
Adults are small but very distinctive, 2.3-2.8mm, elongate-oval and discontinuous in outline, the colour varies and very dark specimens occur but typically the head is dark brown, the pronotum pale to dark orange and the elytra sandy with the suture and a variable spot behind the middle of each dark brown or black, in extreme cases the spot may be very pale or reduced or it may be extensive and reach the lateral margin. Entire dorsal surface finely pubescent. Males are generally smaller than females and less well marked. The antennae are brown, usually with segments 8-10 darker and the legs are pale, as the elytra. Head transverse with large, convex and coarsely-faceted eyes and short temples that converge strongly to a wide neck, vertex and frons strongly and moderately densely punctured, the punctured discreet, frontoclypeal suture distinct and broad and the labrum simply curved anteriorly. Antennae inserted laterally in front of the eyes, 11-segmented and only weakly broadened towards the apex, basal segment long and broad, 2-8 elongate and 9 and 10 quadrate to transverse. Pronotum transverse, broadest in front of the middle and evenly curved to a narrow basal margin, posterior angle with a single small tooth, anterior angles rounded, with three prominent blunt teeth, anterior margin curved and finely denticulate laterally, surface weakly convex and densely punctured. Elytra elongate, about 7:5, with rounded shoulders and lateral margins evenly curved to a continuous apical margin, each with nine strongly punctured striae usually complete to the apex, and weakly convex and very finely punctured interstices. Legs narrow and moderately long, all femora unarmed and widely visible in normal setting, tibiae gradually widened to rounded apices, tarsi 5-segmented, the basal segments strongly lobed, the fourth diminutive and the terminal segment long and curved. Claws smooth and lacking a basal tooth.