Dacne rufifrons (Fabricius, 1775)
POLYPHAGA Emery, 1886
CUCUJOIDEA Latreille, 1802
EROTYLINAE Latreille, 1802
DACNINI Gistel, 1848
DACNE Latreille, 1796
This is a locally common species across southern and central England and eastern Wales, extending north to the north Yorkshire moors but absent from the West Country and the islands. The continental distribution extends from Spain to eastern parts of Russia; in Europe it occurs sporadically from lowland to lower mountain altitudes along the Mediterranean, extending north to Denmark and perhaps also the southernmost parts of Fennoscandia although it may have become extinct here in recent years, through much of this range it is local and rare, becoming common mostly in western and southern regions. In many areas there has been a recent decline-in line with saproxylic species generally-due to woodland exploitation and removal of old trees from urban areas. Adults are present year-round, they become active early in the spring and are nocturnal, they are associated with a range of fungi on deciduous trees such as alder, ash, birch, poplar, oak and lime but they most often occur on sycamore and beech. Typical habitats are open woodland, parkland and gardens where mature trees hosting suitable fungi are present; they almost always occur on standing timber and may be quick to colonize freshly developed fungi, through the winter they may be found under bark or among fungus whereas during the warmer months they may be found active on the surface of wood in the vicinity of fungi. They breed in the spring and eggs are deposited on the surface of fungi, the fungivorous larvae develop inside fruiting bodies, most often Polyporus squamosus (Huds.) Fr. and Fomes fomentarius (L. ex Fr.) Kickx. but adults have been recorded from a range of fungi and so there may be other larval hosts, larvae develop rapidly and are fully grown within a month, new generation adults appearing in early summer. Both adults and larvae will often be found along with other fungus beetles, typically ciids, mycetophagids, salpingids and tenebrionids but also many others, including the closely-similar and equally widespread D. bipustulata (Thunberg, 1781), and so when sampling at night they need to be looked for very carefully.
Adults are small, 2.5-3.0mm, elongate-oval and weakly convex beetles, they may be recognized by the size, colour and general outline; within the family only small specimens of Triplax might be mistaken for Dacne but these are most obviously different in having a loose antennal club and clearly striate, uniformly coloured elytra. There is often overlap in colour between this species and D. bipustulata but here the head and pronotum are dull and microsculptured whereas in bipustulata they are smooth and shiny. Head widely transverse from above, red or pale brown, evenly-convex and finely punctured, antennal inserted in front of the eyes and widely separated. Antennae 11-segmented; three basal segments elongate, 4-7 quadrate, 8 transverse and 9-11 forming an abrupt and compact club. Pronotum transverse, lateral margins very narrowly explanate; rounded anteriorly and slightly sinuate or more or less parallel-sided in the basal half, anterior margin rounded and produced, posterior angles perpendicular and basal margin strongly sinuate. Surface finely punctured throughout, the punctured separated by at least their diameter, on the disc usually by much more, usually extensively dark with the anterior margin pale but specimens with an entirely pale pronotum are not uncommon. Scutellum widely transverse, strongly expanded from the base and rounded apically, usually dark, as the surrounding cuticle, and finely punctured. Elytra extensively dark, with shoulder maculae and sometimes the apical region pale brown, basal margin strongly sinuate, humeral angles sharp and laterally broadest in the basal third then evenly narrowed to a continuously-rounded apex. Punctation random; the punctures less well-defined and a little sparser than those on the pronotum. Legs entirely pale; femora only narrowly visible from above, all tibiae rather strongly expanded to a truncate apex, inner apical margin with a row of stiff pale setae but without obvious spurs. Tarsi 5-segmented with all segments obvious, 1-4 short and lobed ventrally, the terminal segment long and only weakly expanded towards the apex, claws small and very finely toothed at the base.