Limnobaris t-album (Linnaeus, 1758)
This very widespread and generally common Eurasian species occurs from lowland to low mountain altitudes throughout Europe from the Mediterranean north to the UK and above the Arctic Circle in Sweden. The UK distribution is unusual; it is common in the southeast from Hampshire to Kent and as far north as South Hertfordshire, throughout Wales and across the northern half of East Anglia, absent from The West Country and central England generally but scattered and very local in the north, and there are a few records from the south of Scotland and the northern highlands. Typical habitats are all kinds of wetlands, usually on the margins of slow moving or stagnant water but also in fens, marshes and peat bogs, beaches, dunes and salt marshes, floodplains and permanently damp wooded areas where the adults occur from early in the year until July or August. Adults are associated with various sedges (species of Carex L. and Cladium Brown, P.) and rushes (Juncus L.) and may be seen on the flowering spikes early in the season, they are readily sampled by sweeping but generally occur in small numbers although at certain times may be present in great abundance; they occur rather sparsely in marginal situations throughout our local area in South Hertfordshire area but during April 2014 were abundant on sedges along the River Gade at Croxley Common Moor ad Cassiobury Park. Reproduction occurs early in the year and larvae develop among the roots of various sedges, on the continent they have been recorded from bottle sedge (Carex rostrata Stokes, 1787), lesser pond-sedge (C. acutiformis Ehrh.) and also common club-rush (Schoenoplectus lacustris (L.)), eggs are laid in the bases of leaves and larvae feed on leaves before boring down inside the stem to feed in the rhizomes, they complete their development inside the rhizomes, overwinter and pupate within during the following April although adults are also known to overwinter on the continent.
2.8-4.5mm. Entirely shiny black, the dorsal surface with sparse pale narrow scales that leave the cuticle exposed, the prosternum is similarly scaled but the rest of the thorax is largely obscured by dense broad and creamy-white scales; these cover the ascending mesepimera which are narrowly visible from above behind the posterior pronotal angles, a feature which, together with the overall appearance, will distinguish the genus among our UK fauna. The only confusion might be with the closely-similar L. dolorosa (Goeze, 1777), here the elytral scales are longer and overlap whereas in the present species they are shorter and do not overlap but they are often missing in older specimens and in any case this feature may be difficult to appreciate but the form of the aedeagus is distinctive; in dolorosa the median is broad, curved laterally and the apex is bluntly-pointed, in t-album it is narrow, parallel-sided and evenly rounded apically. Head transverse with weakly-convex eyes that follow the outline and a long parallel-sided rostrum which is continuous with the frons and not demarked by a transverse impression, the vertex evenly convex and finely and sparsely punctured. Antennae inserted beyond the middle of the rostrum in both sexes; scape thickened towards the apex, funiculus 7-segmented and the club broadly-oval. Pronotum slightly transverse, parallel-sided or narrowed towards the base and curved towards a narrow apical margin, densely and strongly punctured although usually with a narrow smooth median line, basal margin produced weakly behind the scutellum. Prosternum with widely separated coxal cavities but lacking a rostral channel. Scutellum quadrate and broadly-rounded. Elytra with prominent humeri, curved laterally, separately rounded apically and completely covering the pygidium, with striae well-impressed to the apex and flat interstices, each with a row of punctures bearing a short white setae. In lateral view the dense creamy-white scales on the mesepimera and towards the lateral margins of the metasternum form a T-shape; t-album. Abdomen variably scaled, often sparsely so, sometimes rather densely but the underlying cuticle is substantially visible.