Omalium laeviusculum Gyllenhal, 1827

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POLYPHAGA Emery, 1886

STAPHYLINOIDEA Latreille, 1802

STAPHYLINIDAE Latreille, 1802

OMALIINAE MacLeay, 1825

OMALIINI MacLeay, 1825

Omalium Gravenhorst, 1802

This western Palaearctic species is restricted to the coasts of northern Europe from France to the far north of Norway and extending into western Russia although it is absent from some of the southern Baltic countries, it extends north to the UK, Faroe and Iceland and is very local and sporadic throughout, there are older records from inland wetland habitats in Europe but these are now thought to be based on misidentifications. In the UK it occurs sporadically around the coasts of England, Wales and Scotland north to Orkney and is common along the eastern coast of Northern Ireland, it is most prevalent in the west and seems to be absent from much of the east coast of England. Although rather local they tend to be abundant where they occur, adults may be found among seaweed along the strand line or under stones and drift wood and on warm sunny days they can be seen flying or even swarming over stranded seaweed. Adults seem to be active year-round as they are often active under seaweed through the winter, they also occur in buried seaweed and may be abundant among decaying vegetation along the upper foreshore e.g. we found them in abundance, along with numerous other beetles, among huge masses of seaweed collected from public beaches and dumped on waste ground in North Somerset. Little is known of the biology but they are probably typical of the family with predatory larvae developing through spring and summer among decaying organic matter and new generation adults appearing in the summer.

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4-5 mm. Adults may be distinguished from other maritime species by the flattened and broadly elongate form and distinctive colouration; head black, body otherwise reddish-brown, often with obscure darker areas to the pronotum and elytra, legs pale brown, antennae dark with at least some basal segments pale. Head transverse with protruding convex eyes and strongly converging temples, surface with linear microsculpture, vertex with an ocellus each side behind an oblique depression extending towards the anterior margins of the eyes, clypeus and frons smoothly convex, basal segment of maxillary palps curved at the base and broadened to the apex, penultimate segment much shorter and at most only slightly broader, terminal segment elongate and fusiform. Antennae inserted laterally outside the base of the mandibles, segments 1-7 elongate, segments 8-11 shorter and slightly broader. Pronotum transverse, broadest in front of the middle and curved anteriorly, lateral margin sinuate before perpendicular posterior angles, basal margin slightly curved, surface sparsely and finely punctured and quite strongly microsculptured throughout, flattened towards the lateral margins and with a broad elongate depression either side on the disc. Scutellum triangular with straight sides, surface with fine elongate microsculpture. Elytra quadrate or only slightly elongate, distinctly broader across the rounded shoulders than the base of the pronotum, slightly dilated before widely rounded posterior angles and separately curved apical margins, surface sparsely and finely punctured and microsculptured throughout and often with several larger setiferous punctures along the disc. Abdomen about as long as the elytra, broad and narrowed to the apex, four basal tergites strongly bordered, apical tergite triangular and not obviously bordered, surface of all tergites very finely punctured. Legs long and slender, the femora widely visible in normal setting, tibiae finely pubescent and without obvious apical spurs. Tarsi 5-segmented, the terminal segment about as long as the others combined.

Omalium laeviusculum 1

Omalium laeviusculum 1

Omalium laeviusculum 2

Omalium laeviusculum 2

Omalium laeviusculum 3

Omalium laeviusculum 3

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