Hypulus quercinus (Quensel, 1790)
This is a widespread European species extending from the Mediterranean north to Fennoscandia and the UK and east into western Russia. Here it is very local, occurring throughout Wales and sporadically in the south of England although it may be common where it occurs. The typical habitat is old established woodland with plenty of large oaks in various stages of decay; they are mainly associated with oaks but have also been reported from red-rotten wood in old hazel trunks, on the continent they are also associated with oak while H. bifasciatus is known to develop in a range of broadleaf trees. Adults are mostly crepuscular and nocturnal but have been swept from vegetation beneath oaks or around fallen trunks and also from oak foliage during the day, at night they may be observed on old and dry trunks, particularly where the bark is missing, or among well-decayed and crumbly xylem in fallen trunks and branches, when disturbed they move slowly into cracks or accumulated debris or they may remain still for long periods and so are easily observed. Adults emerge during April and May and persist into June or July, they tend to remain among the wood from which they emerged and so large accumulations may develop in a small area of woodland, mating occurs from early in May and is followed by dispersal by flight, hence a group of adults may be present for a few weeks and then suddenly vanish. Oviposition occurs soon after mating, eggs are laid into decaying xylem and the resulting larvae burrow through this substrate, often entering intact wood around the margins of rot-holes and hollows, they develop through the spring and summer and pupate among the wood in late summer and autumn, adults eclose in the autumn but remain in their pupal cells until the following spring. Our only encounter with this species was in local woodland where a large population was found nocturnally on the surface of a fallen oak trunk, adults were scattered as singles or pairs and several mating pairs were observed in early May, they persisted for several weeks before vanishing.
5.5-7.0mm. This elongate and narrow species very distinctively patterned and easily recognized in the field; head and pronotum dark, elytra dark with characteristic pale bands, all appendages pale. Head transverse, with widely transverse and weakly convex eyes that curve around the antennal insertions, vertex densely and quite strongly punctured, and the entire surface with pale-golden recumbent pubescence. Antennae 11-segmented and filiform; segment 2 quadrate, the remainder elongate, insertions visible from above; longer in the male but in both sexes reaching back to the basal third of the elytra. Pronotum dark with at least the anterior margin pale, the basal margin often extensively so, quadrate and broadest at or in front of the middle and sinuate to sharply-acute posterior angles, basal margin widely bi-sinuate and anterior margin rounded. Surface strongly and densely punctured, often confluently so towards the base, pale pubescence quite dense in the basal half but sparse or absent towards the apex, basal fovea deeply impressed and long, reaching almost to the middle. Elytra parallel-sided or widest behind the middle, more noticeably so in the female, and narrowed to separately rounded apices, the suture strongly bordered, otherwise without striae, surface strongly and densely punctured and with pale-golden pubescence lying in various directions but mostly oblique along the suture. Colour and pattern distinctive for this species. Legs long and robust; tibiae gradually broadened to truncate apices, each with two short spurs on the inner angle. Tarsi 5-5-4, pro-tarsomeres 2-4 bilobed, much more strongly so in the male, penultimate meso- and meta-tarsomeres deeply lobed. Claws fine and smooth internally. Males are generally smaller than females and have the terminal maxillary palpomere broader.
Hypulus Paykull, 1798
This is a small genus of about 10 species, and with a single exception they have a Palaearctic distribution. H. actangulus Lewis, 1895, H. cingulatus Lewis, 1895 and H. higonius Lewis, 1895 are endemic to Japan, H. bifasciatus (Fabricius, 1792) and H. quercinus (Quensel, 1790) have a temperate Eurasian distribution and the remainder, with the exception of H. simulator Newman, 1838 which occurs in the north-eastern United States, occur in Asia. Of the European species, H. bifasciatus is a central and northern species extending to Fennoscandia but absent from the UK while H. quercinus is more widespread.