Atomaria mesomela (Herbst, 1792)

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POLYPHAGA Emery, 1886

CUCUJOIDEA Latreille, 1802

CRYPTOPHAGIDAE Kirby, 1826

ATOMARIINAE LeConte, 1861

ATOMARIINI LeConte, 1861

Atomaria Stephens, 1829

Anchicera Thomson, C.G., 1863

Widespread across the Palaearctic region, but in Europe a mostly central and northern species it is locally common from northern parts of Spain and Italy to Ukraine in the south and reaching north into the UK and southern provinces of Fennoscandia although there are a few records further north to the Arctic Circle, it is generally absent from the Mediterranean islands and North Africa but it does occur in the Canaries. There are also records from California which if correct seem to represent the only North American site for the species. In the UK it is widespread and locally common throughout Southern and Central England and Wales, including all the islands, although it tends to be mainly coastal in the West Country and much of Wales, and extends north into southern Scotland where it is very local and generally scarce. Also widespread in Ireland though very local and mostly coastal or near coastal. This is essentially a wetland species; adults often occur among damp layered leaf-litter and tussocks in marshes or about the edges of ponds and rivers and sometimes in old reed or rush stems, they usually occur in numbers and may swarm in late spring or early summer. In Northern Europe they are recorded from all types of wetlands, including peat bogs and also occur in damp meadows and among accumulated organic matter such as grass clippings in damp situations, including domestic gardens. Adults are present year-round although they are rarely recorded in the winter; they are active from April until October and peak in abundance during June and July. This is among the most common and widespread of our hygrophilous species but little is known of the biology. Adults may be found at any time by sieving or extracting suitable material and they sometimes occur among flood-refuse. So far as is known adults are consistently short-winged.

Atomaria mesomela

Atomaria mesomela

© Lech Borowiec http://www.cassidae.uni.wroc.pl/Colpolon/index.htm

1.3-1.7mm. Elongate-oval and discontinuous in outline, glabrous and shiny black or dark brown but for the elytra which are abruptly bicoloured dark in the basal half and reddish behind the middle, appendages pale  reddish except for the antennal clubs and last tarsal segment which are partly or wholly darker. Pronotum and elytra moderately strongly and closely punctured, the punctures for the most part separated by about their own width. Antennae long and slender with the club only slightly wider; segment 9 and 10 quadrate to slightly elongate and the terminal segment elongate and pyriform. Pronotum transverse, broadest near the middle and distinctly and rather strongly narrowed to obtuse posterior angles and rounded anterior angles (from above), basal margin straight and distinctly bordered, surface evenly convex and only weakly depressed before the base. Pronotal surface smooth but for weak microsculpture towards the sides and base, pubescence oriented forward in the basal half, backwards in the apical half and mostly transverse across the middle. Scutellum widely transverse. Elytra elongate and smoothly and usually rather strongly curved from sloping shoulders to a continuous apical margin, without striae and mostly smooth and shiny, in typical specimens sharply bicoloured; the colours generally separated horizontally across the middle but this is variable. In rare cases the elytra may be substantially or wholly black but here there is usually a paler area or spot before the apex which becomes obvious under strong light. Legs long and slender, fore tibiae straight and without a ventral ridge. Tarsi 5-segmented; the basal segments short and weakly lobed and the terminal segment long and curved.