Haliplus laminatus (Schaller, 1783)
This is a generally scarce central and northern European species which extends sporadically west as far as northern Spain and south into northern Italy and the Balkans, further east it is present in Asia Minor and the Near East and it extends into western Russia, the northernmost limit is the south of Sweden where it is known from only a few localities, and in the UK it is locally common in Central and Southern England although there has been a general decline in the west of this range over recent decades. Adults have been recorded year-round; they are typically active over a long season from early in the year until the autumn and they will often be found with other members of the genus. They occur in still or slow-moving waters with patchy or sparse vegetation, usually in slow sections of rivers and streams over fine silt or clay substrates but also in artificial habitats such as canals, drainage ditches, reservoir and gravel-pit margins and ponds. Little is known of the biology but both adults and third-instar larvae have been found overwintering out of the water, larvae feed on filamentous algae while adults also consume algae but are more generally predatory, feeding on small insect eggs and larvae etc. The larva has been described by van Vondel (1986).
2.5-3.3mm. Within the subgenus Liaphlus Guignot, 1928, which may be recognized by the lack of pronotal grooves and generally smooth body surface, this species is distinguished by the elytral humeri which are rounded and much wider than the base of the pronotum, and the dark yellow body colour. Dorsal surface greyish-yellow with the head and elytral striae at least to some extent darkened and the elytra often with two indistinct transverse bands formed by variation in the strength of the strial darkening. Pronotum rounded and narrowed laterally from acute posterior angles, surface lacking fine basal grooves, with scattered larger punctures towards the margins but substantially smooth on the disc. Elytral broadly and near parallel-sided in the basal third, humeri wide; the angle formed with the base of the pronotum almost perpendicular, interstices smooth in the male and very finely micropunctured in the female (X40). Males may be distinguished by the strongly sinuate outer margin of the basal meso-tarsomere. The broad form may be suggestive of Peltodytes but here the apical maxillary palpomere is longer than the penultimate segment while in the present species it is much smaller.