Homalota plana (Gyllenhal, 1810)

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POLYPHAGA Emery, 1886

STAPHYLINOIDEA Latreille, 1802

STAPHYLINIDAE Latreille, 1802

ALEOCHARINAE Fleming, 1821

HOMALOTINI Heer, 1839

Homalota Mannerheim, 1830

This is a mostly northern Palaearctic species, it occurs throughout the region, extending south into North Korea, and is generally common in Europe from France through northern Italy to Asia Minor and in the north To the UK and the far north of Fennoscandia, occurring from lowlands to mid-mountain altitudes. It has also become established across the northern United States and parts of eastern Canada following accidental introductions during the twentieth century, In the UK it is locally common across England and Wales north to Yorkshire, though absent from the West Country and there are a few scattered records further north to the Scottish Highland and from Northern Ireland. In the UK adults occur under bark of various broad-leaved trees, usually where it is recently dead and still tight fitting and moist, they are often recorded from Beech (Fagus sylvatica L.), poplars (Populus L.) and willows (Salix L.) but also from oak (Quercus L.), elm (Ulmus L.) and other trees, the condition of the bark probably more important than the species. On the continent is also appears under the bark of various conifers, especially pine (Pinus L.), spruce (Picea Mill.) and larch (Larix Philip Miller), and often where these are attacked by bark beetles or other subcortical insects. Little is known of the life cycle but adults occur year-round, they peak in abundance during spring and autumn and are common through the winter, they are known to be detritivores and are sometimes found among masses of subcortical hyphae. In south Herts. we find them commonly under damp willow and poplar bark, mostly on fallen timber, and often in company with Siagonium quadricorne Kirby, 1815, Uleiota planatus (Linnaeus, 1761) and Silvanus spp.

Homalota plana 1

Homalota plana 1

Homalota plana 2

Homalota plana 2

© U.Schmidt

Homalota plana 3

Homalota plana 3

© Lech Borowiec

2.3-4.5 mm. Body very flattened, elongate and parallel-sided, body dark brown, usually with the abdomen a little darker, legs pale brown, antennae pale to dark brown. Head slightly elongate and slightly narrower than the pronotum, with weakly convex eyes and long evenly-curved temples, surface evenly convex, with granular microsculpture and fine punctures, the pubescence lying longitudinally along the centre and horizontally across the disc, mandibles prominent and curved, penultimate maxillary palpomere expanded, terminal segment very thin by comparison. Antennae 11-segmented and gradually broadened to the apex; segments 1-3 elongate, 4 quadrate and 5-10 transverse, apical segment shorter than 9 & 10 combined and rounded apically. Pronotum transverse and narrower than the elytra, broadest in the apical third and narrowed to distinct posterior angles and rounded anterior angles, apical margin straight, basal margin oblique laterally and straight across the middle. Pronotal surface with strong granular microsculpture and very fine punctures, pubescence forming arcuate transverse patterns from the centre in the apical half but more horizontal towards the base, in most specimens the surface has a shallow and broad impression along the centre but this is variable. Elytra slightly transverse, with rounded shoulders and dilated to distinct posterior angles, surface microsculptured and with moderately dense oblique pubescence. Abdomen strongly bordered and almost parallel-sided, tergites 3 to 6 transversely impressed, the tenth with a subquadrate medial patch of setae with 3 setae on each side, basal tergites moderately strongly punctured, apical tergites more finely so, and all tergites with very fine granular microsculpture. Hind femora longer and broader than the others, front tibiae with two fine erect setae on the outer margin; one near the apex and one about the centre, middle and hind tibiae with a single erect seta before the middle. Tarsi 4-4-5. Basal segment of front tarsi as long as the second, basal segment of the middle tarsi slightly longer than the second segment, terminal segment of all tarsi long and slender. Claws smooth and very fine, without a basal tooth or empodial setae.