BIPHYLLIDAE LeConte, 1861
False Skin Beetles
Biphyllus lunatus occurs commonly throughout England and Wales among coal fungus on ash, while Diplocoelus fagi is a very local species restricted to the south.
POLYPHAGA Emery, 1886
CUCUJOIDEA Latreille, 1802
Biphyllus Dejean, 1821
Diplocoelus Guérin-Méneville, 1844
A relatively small family of about 190 species included in 7 genera. They have a worldwide distribution with the largest diversity (66 spp.) in the Neotropics. In the Northern Hemisphere diversity falls rapidly with latitude; in the United States there are 2 genera and 3 species. They are generally woodland insects with the adults and larvae occurring together and although the early stages of most species are poorly understood it is very likely that most are mycetophagous, feeding upon and living within dendrophilous fungi. Two genera are represented in the U.K; Biphyllus Dejean, 1821 and Diplocoelus Guérin-Méneville, 1844, each by a single species.
Byphillids are small, <5mm, and rather drab species; most are brown or grey with pale or orange markings. The habitus is typified by the U.K. species; elongate-oval with a relatively large head, prominent eyes that often have large facets, and the entire dorsal surface with short pubescence. The pubescence is generally erect, short and curved so that it is visible in outline along the pronotal and elytral margins. The antennae are 11-segmented with a distinct 2 or 3-segmented club and inserted under the front margin of the head. The terminal segment of the maxillary palps is cylindrical, that of the labial palps are dilated and transverse. The pronotum is transverse and bearing one or two lateral longitudinal ridges parallel to the side margin. Scutellum distinct. Elytra with regular striae, including a scutellary stria, consisting of strong punctures. Elytral epipleurs distinct. Tarsi 5-5-5 without any obviously lobed segments. Last segment very long. Claws simple. The larvae are almost cylindrical with distinctly pigmented tergites and small conical urogomphi.
Both our U.K. species were formerly included in the Erotylidae but are easily distinguished by the pronotal ridges and the lack of obviously bilobed tarsal segments. Both are keyed out in Joy’s handbook; Biphyllus (as Diphyllus) in the Nitidulidae, and Diplocoelus in the Cryptophagidae. Biphyllus can be identified by the elytral marking while Diplocoelus is rather drab brown but the pronotal sculpture, strongly punctured elytra and simple tarsi will serve to identify both species.
Dark brown to black, each elytron with a transverse, angled patch of pale pubescens near the middle and often a sub-apical patch. Pubescence more evenly recumbent throughout. Antennal club 2-segmented. [Some specimens have small patches of pale pubescence to the pronotum and a pale humeral mark.]
(Chevrolat in Guérin-Méneville, 1837)
Dark to pale brown, elytral disk often darker. Pubescence on pronotum and elytra uniformly pale; both recumbent and semi-erect hairs present on the elytra. Antennal club 3-segmented.
Biphyllus lunatus is a very local and generally rare species in southern and central Europe and is considered to be threatened in many countries; it is widespread across North West Africa and extends east into southern Siberia and north into the UK and southern Fennoscandia. In the UK it is locally common throughout England and Wales though less so in the north and there are a very few records from southern Scotland. The species is usually associated with the fungus Daldinia concentrica (Bolton) Cesati & de Notaris, which grows mainly on ash (Fraxinus excelsior L.) and much less often on other broadleaf trees such as alder (Alnus Mill.) and birch (Betula L.), adults occur year-round and are rarely seen away from the fungus and so may be under-recorded. Older fruiting bodies that have begun to crumble can be pulled apart or prized away from the wood to find the beetles but this should be done sparingly as the larvae develop within and will often be seen alongside the adults. Keeping samples of the fungus is a good way of obtaining adults and, as pupation occurs within the fungus, samples of all stages can be found with regular inspection. On the continent adults have also been found in galleries of the bark beetle Hylesinus crenatus (Fabricius, 1787).
Diplocoelus fagi is a mainly central and southern European species which also occurs in North Africa; to the north it extends to the UK and southern provinces of Fennoscandia and it is generally very local and scarce throughout this range. It is widespread though local and seldom common across southeast and central England north to Nottingham, it occurs in deciduous woodland and wooded parkland and gardens etc, and is associated with various fungi on a range of trees; more especially oaks, maples, lime and elm but also many others. Adults are nocturnal and usually occur in the vicinity of fungus, they are present year-round although they never seem to peak in numbers and (at least around Watford) they regularly occur in extraction samples from fungus and dry bark, they otherwise spend their time under bark and among fungi in which the larvae develop through the summer. On the continent they are often associated with the fungus Nectria cinnabarina (Tode) Fr., (1849), a coral spot species that causes cankers on a range of broadleaf trees. Taking likely samples for extraction is the easiest way to record the species although they may occur on the surface of fungoid trunks and fallen timber at night and sieving bundles of twigs from beneath likely trees will sometimes produce adults in numbers.