Anisotoma glabra (Fabricius, 1787)

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POLYPHAGA Emery, 1886

STAPHYLINOIDEA Latreille, 1802

LEIODIDAE Fleming, 1821

LEIODINAE Fleming, 1821

AGATHIDIINI Westwood, 1838

Anisotoma Panzer, 1797

This species occurs throughout most of Europe although in central and southern regions it is rare and mostly confined to montane areas, to the north it extends to the UK, Denmark and far beyond the Arctic Circle in Fennoscandia, the stronghold seems to be Southern and Central Sweden and Finland and the eastern Baltic countries where it is generally common, and to the east it extends through Russia into Central Siberia. In the UK it is locally common in the Scottish Highlands below Inverness and there are a very few (unconfirmed) records from Northern and Central England. The typical habitat is extensive established conifer or broadleaf woodland, usually in mountain areas or in open bog habitats in lower river valleys but in the north also in lowland areas. Adults have been recorded from a wide range of broadleaf trees, most frequently birch (Betula L.), alder (Alnus Mill.), Aspen (Populus tremula L.) and oak (Quercus L.), and in the north they are often common on pine (Pinus L.) and spruce (Picea Mill.) They are active from April until August or September and it is likely that this is the only stage to overwinter, they spend most of their time under bark or among host tissue but they are active at night on the surface of decaying wood and they disperse by flight on warm evenings. Reproduction occurs in spring and early summer and larvae develop and pupate among slime moulds (Mycetozoa, and frequently in false puffballs, Enteridium lycoperdon (Bull.) M.L. Farr, 1976) to produce new adults in late summer. Adults are also associated with slime moulds, on which they are known to feed, but they also frequent a wide range of sporocarps, especially those of Fomes fomentarius (L.: Fr.) Fr. developing on a range of deciduous trees, and they often occur among masses of subcortical mycelia. Searching decaying timber at night, especially in late spring when they tend to be most active, is a good way to record the species but adults also occur among decaying leaf-litter and accumulated mosses below suitable host trees.

Anisotoma glabra

Anisotoma glabra

© Lech Borowiec

3.0-4.8 mm. Broadly oval and rounded, convex above and continuous in outline. Body shiny black with the mouthparts, a spot on the vertex and often the pronotal margins reddish-brown. Ventral surface and legs reddish-brown, antennae pale with segments 7, 9-10 and the base of the terminal segment black. Head transverse, finely punctured and rather flat between large and protruding eyes and with long, converging temples. Antennae inserted laterally in front of the eyes, 11-segmented with a long and loose 5-segmented club, segment 8 diminutive between transversely expanded segments 7 & 9. Pronotum widely transverse, broadest across rounded posterior angles and narrowed to rounded and slightly projecting anterior angles, basal margin straight across the centre and curved laterally towards the angles, apical margin curved. Pronotal surface very finely punctured, evenly convex and without depressions or structure. Elytra narrowly explanate and smoothly curved from rounded shoulders to a continuous apical margin, surface glabrous, finely punctured throughout, with regular punctured striae from the base and a deeply impressed sutural stria from the apex into the apical third or half. Legs short and narrow with femora not visible in normal setting. Tibiae only weakly broadened from the base, front tibiae with only fine setae along the external margin, middle and hind tibiae with rows of stiff spines externally and strong apical spurs. Tarsi 5-5-4 in males, 5-4-4 in females.