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Cordicollis instabilis (Schmidt, 1842)
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POLYPHAGA Emery, 1886
TENEBRIONOIDEA Latreille, 1802
ANTHICINAE Latreille, 1819
Cordicollis Marseul, 1879
This very local maritime species occurs around the coast of England from the Wash to Dorset, including the Isle of Wight, and is also known from a few more widespread records including one from Cardiganshire. Although the species is local it is usually abundant where it occurs; adults are active over a long season from March or April until November and overwinter in the soil or under debris in sheltered situations. Typical habitats are exposed areas of sand or mud on salt marsh margins although they also occur among sparsely vegetated areas further from the beach and have been recorded under accumulated seaweed above the tide line. Adults are diurnal and crepuscular; they sometimes run on bare soil in hot weather but they mostly remain under debris or among tussocks etc during the day and become active in the evening. Both adults and larvae are saprophagous and larvae develop among decaying plant material during the summer. This is otherwise a widely distributed western Palaearctic species; it is present in the south of Sweden and Norway but otherwise absent from the Baltic countries, it is yet to be confirmed from Poland but is then known more-or-less continuously from the coasts of Denmark and Germany to the Black and Caspian Seas, it occurs on most of the Mediterranean islands, it is widespread across coastal North Africa and is known from the Azores and Canary Islands. The nominate subspecies occurs throughout the area including the UK, but two further subspecies, C. i. franzi (Bonadona, 1954) and C. i. geminipilis (Desbrochers des Loges, 1875) are known from the coasts of Spain.
3.0-4.3 mm. Males are easily distinguished by the form of the hind tibiae, females can be difficult but the near-parallel temples and truncate base of the head are distinctive with experience. Body dark reddish-brown to creamy-brown, often with various paler markings to the elytra, legs brown with the femora darker, antennae paler brown. Entire dorsal surface with rather dense recumbent pubescence. Head with prominent, almost hemispherical eyes and long, parallel temples, base broadly curved and bluntly pointed medially; surface evenly convex and densely but discretely punctured except for a narrow smooth area in front of the base. Maxillary palps securiform and antennae filiform in both sexes. Pronotum quadrate or nearly so; broadest towards a rounded anterior margin and narrowed to a sub-basal constriction, basal margin almost straight, surface weakly convex and strongly and densely punctured. Elytra much wider than the pronotum, with broadly rounded shoulders and lateral margins curved to separately rounded apical margins, surface without striae but densely and moderately strongly punctured, becoming more finely so towards the apices. The elytral colour is very variable, often completely brown but sometimes bicoloured with the basal half paler, often with paler markings across the base and before the apex. Legs long and slender, the hind tibiae expanded towards the apex in the male, normal in the female, all with tiny, hardly discernible apical spurs. Tarsi 5-5-4, the penultimate segment deeply bilobed, male front tarsi generally broader than those of the female. Claws smooth and only very weakly toothed at the base.