Abraeus perpusillus (Marsham, 1802)
POLYPHAGA Emery, 1886
HYDROPHILOIDEA Latreille, 1802
ABRAEINAE MacLeay, 1819
Abraeus Leach, 1817
This species is widespread and generally common across central and southern Europe but rather sporadic and much more local in northern areas where it extends into northern Russia, Fennoscandia and the UK, it is also widespread in northern Africa, Asia Minor and south-western Asia. In the UK it is locally common across lowland England north to Nottingham though very local and generally rare in the West Country, Wales and further north to York. Adults occur year-round and are active over a long season from very early in the spring, they overwinter among dead wood or under bark etc; we have extracted them from old bird nest material and they often appear in winter flood refuse from the river Colne in Watford, they are nocturnal and among the first species to appear on wood in late winter or early spring. Typical habitats are damp deciduous woodland and parkland with plenty of fallen and decaying wood, they usually occur in numbers and may be found on any dead wood but they are strongly attracted to the sawn ends of recently felled trunks and branches and will often appear alongside saproxylic ants such as Lasius brunneus (Latreille, 1798) or, on the continent, species of Camponotus Mayr, 1861. They remain active until late in the autumn and may be observed on damp decaying wood or at sap on trunks and fallen branches in parks and undisturbed gardens generally and through the colder months they regularly appear in extraction samples taken from bark and tree hollows. Little is known of the biology but adult populations peak in June or early July, at least around Watford, and when large aggregations of adults appear on cut branches or stumps at night they are almost certainly grazing micro-fungi, and they often do so among numbers of Cartodere nodifer (Westwood, 1839).
Abraeus perpusillus 1
© U.Schmidt www.kaefer-der-welt.de
Abraeus perpusillus 2
© Lech Borowiec http://www.cassidae.uni.wroc.pl/Colpolon/index.htm
Adults are tiny globular beetles, glabrous and entirely shiny black to reddish-brown with paler appendages, there are a few superficially similar histerids that occur in similar situations but the present species may be recognized by the form of the front tibiae, and anyway with experience they become obvious in the field. 1.0-1.5mm. Elongate-oval and continuous in outline (with the head retracted), entire dorsal surface finely and quite densely punctured and very finely microsculptured. Head transverse with weakly convex eyes only narrowly visible from above, fronto-clypeal area broadly depressed and labrum rounded anteriorly, mandibles broad, curved and with a strong internal tooth. Antennae inserted before the eyes, 11-segmented with a broad and curved scape and elongate-oval club. Pronotum rounded from acute posterior angles, basal margin slightly produced medially, surface simply convex and without fovea etc, Elytra broadest around the basal third and narrowed to truncate apical margins which leave the pygidium and pro-pygidium exposed, without any trace of striae above or on the epipleura. Middle and hind legs long and slender with tibiae slightly angled externally, front tibiae greatly dilated from a narrow base; the outer margin sharply angled and with a small tooth on the anterior edge-along with the general appearance this will identify the species among our fauna. Tarsi 5-segmented and simple.