Euglenes oculatus (Paykull, 1798)

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Genus:

POLYPHAGA Emery, 1886

TENEBRIONOIDEA Latreille, 1802

ADERIDAE Csiki, 1909

Euglenes Westwood, 1830

This is a mostly Western and central European species, it is the commonest of the five European species but nonetheless generally very local and scarce, extending from the Pyrenees in Spain to Italy and Austria in the south and north to Denmark, the UK and a few southernmost provinces of Sweden and Norway. The precise distribution is not known as it was formerly confused with the closely similar E. pygmaeus (De Geer, 1774), which has a similar distribution but is not known from the UK, and it is thought to have decreased in range and abundance over recent decades. In the UK it is widespread though very local across England north to the Humber and across South Wales but otherwise very sporadic and rare. Adults have been recorded throughout the year but are usually active from May until August or September, peaking in abundance during June and July. Typical habitats are  ancient deciduous woodland and wooded parkland with older trees in various stages of decay although they also occur on isolated mature trees on grazing pasture etc. and isolated specimens have been recorded far from suitable habitats. The species is associated with a range of deciduous trees but most records are from ancient decaying oaks where the larvae are known to develop among damp and fragmented heartwood. Adults are mostly nocturnal but they also visit blossom, mostly elder (Sambucus nigra L.) but also hawthorn (Crataegus Tourn. Ex L.) and others, and sometimes in numbers. By day they mostly remain under bark or in crevices, they are active on trunks and fallen timber at night and they often fly around host material on warm spring and summer evenings. Searching timber at night or beating blossom by day are the best ways to find adults but they sometimes occur in flight-interception traps and they come to UV lights placed in suitable situations.

Euglenes oculatus 1

Euglenes oculatus 1

© Lech Borowiec

Euglenes oculatus 2

Euglenes oculatus 2

© Udo Schmidt

2.1-2.6 mm. Elongate and discontinuous in outline with the head and elytra wider than the pronotum, dorsal surface with fine pale pubescence throughout, forebody dark brown to black, elytra and appendages pale brown. Head transverse, with large convex and pubescent eyes that almost meet anteriorly and short rounded temples. Terminal maxillary palpomere widely securiform. Antennae filiform or very weakly serrate; in males much longer and with the terminal segment truncate, in females shorter and with the terminal segment rounded. Pronotum transverse, broadest about the base and slightly narrowed to rounded anterior angles, posterior angles obtuse and basal margin sinuate, surface finely but not densely punctured throughout and with (usually) indistinct impressions towards the base. Scutellum transverse; widest across the base and narrowed to a truncate apex. Elytra slightly dilated from rounded shoulders to a continuous apical margin (although the sutural margins often diverge towards the apex) which usually leaves the last abdominal tergite exposed.  Surface without striae, densely and moderately strongly, in places confluently, punctured throughout. Legs long and slender with simple femora and tibiae without obvious apical spurs. Tarsi 5-5-4, although in each case the penultimate segment is diminutive and often partly hidden within the narrowly bilobed previous segment and so they often appear to be 4-4-3, the basal segment about as long as the others combined. Claws smooth and without, or with only a very weak basal tooth.