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Megapenthes lugens (Redtenbacher, 1842)







POLYPHAGA Emery, 1886


ELATERIDAE Leach, 1815

ELATERINAE Leach, 1815

MEGAPENTHINI Gurjeva, 1973

Megapenthes kiesenwetter, 1858

This is a very local and rare western Palaearctic species, it is known from Spain to Italy and Ukraine in the south and extends north into Germany, where it is considered to be critically endangered, and the UK, it is known from only a very few sites in northern Europe and is absent from Denmark and the Baltic countries generally. This European distribution is not continuous and it is missing from certain areas such as Switzerland and the Netherlands. Beyond this it is known from the Caucasus, parts of western Russia and northwest Africa. In the UK it is known from only a few sites in Hampshire and Berkshire although it may still be present in Gloucestershire, it was formerly much more widespread with 19th century records from Essex, Surrey, Middlesex and Norfolk but seems to have declined through the 20th century. Adults are active during May and June or, in warmer continental regions, until August although overwintering specimens have been recorded much earlier. Typical habitats are old established woodland with plenty of fallen timber and trees in various stages of decay. Adults spend much of their time among standing or fallen decaying wood, they are occasionally active in bright sun on the warmest of days but are mainly crepuscular and nocturnal, at which time they take flight to find flowering shrubs such as Hawthorn (Crataegus monogyna Jacq.) or Elderberry (Sambucus nigra L.) where they feed on pollen. Larvae develop in decaying wood, usually in hollow trunks and branches; in the UK they have been recorded from elm (Ulmus L.) and beech (Fagus L.), and we have recorded adults under bark on a fallen oak (Quercus L.) trunk, but on the continent also from poplar (Populus L.), alder (Alnus Mill.), ash (Fraxinus L.) and chestnut (Castanea Mill.) and there seem to be no records of coniferous species. Larvae are usually quoted as being predatory on other wood boring beetles and their larvae, on the continent they have been recorded preying on larvae of the longhorn beetle Rhamnusium bicolor (Schrank, 1781) and in the UK they are thought to consume larvae of cossonine weevils, development continues through the summer and pupation occurs in the autumn. Adult beetles are fully formed by the autumn but they remain within the pupal cell until the spring.

Megapenthes lugens

Megapenthes lugens

7.5-10.5 mm. Very typical of the family; elongate with a relatively small head, robust pronotum and long and gradually tapering elytra, body with short and extremely fine grey pubescence, entirely dull black to dark grey or with a faint bluish reflection, antennae dark grey with the apex of the terminal segment pale, legs dark grey or brown but the femoral apices, tibial bases and tarsi often to some extent pale. Head smoothly convex and finely punctured between weakly convex eyes, without depressions or a median furrow. Antennae moderately long, reaching back to the pronotal base, serrate from segment four which is longer than segments two and three combined. Pronotum slightly elongate, evenly curved laterally to a rounded anterior margin and widely sinuate before posterior angles which protrude well beyond the middle of the basal margin. Surface evenly convex across the disc and flattened towards the base, finely and densely punctured and shagreened, with a strongly-raised oblique ridge inside each posterior angle and a weak median longitudinal impression in the basal quarter. Basal pronotal margin with two flat tubercles in front of the scutellum which is punctured and cross-rugose. Elytra smoothly narrowed from rounded shoulders to separately-curved apical margins, the lateral quite strongly bordered, especially towards the base where it may give the impression of denticulate shoulders from above, striae narrow, punctured and complete to just before the apex, interstices roughly sculptured; granulate and appearing cross-rugose, especially towards the base. All tarsi with five simple segments, the fourth segment of the middle and hind tarsi only a little shorter than the third segment. Claws smooth, the front claws with a small and obtuse basal tooth and the middle and hind tarsi untoothed.

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