Biphyllus lunatus (Fabricius, 1787)
Widely distributed throughout England north to s.Yorkshire but with records only for the eastern parts of Wales. Adults are found beneath the fruiting bodies of Daldinia concentrica, the round hard black fungus found on decaying Fraxinus (Ash) wood. They are found throughout Watford, occasionally in winter but start to appear in numbers during April or May depending on season. Often several adults are found under a single fungus and sometimes in company with other species e.g. Mycetophagus atomarius Fabricius. The species is common south of Watford along the Colne valley through Rickmansworth to Uxbridge and Cowley. When searching for the species the fungus should be removed carefully from the wood although this is usually difficult as they are hard and well attached and the beetles will be obvious either against the fungus or the wood, although in most cases a layer of fungus usually remains on the wood. Absence of the species should not be too disappointing, the fungus should be kept and stored in the warm as the larvae pupate within .

A very distinctive species that will not be confused with any other. 3-3.5mm. Antennae brown, 11 segmented with a two segmented club; penultimate segment equilateral, terminal segmant oblate. Mandibles prominent. Head punctured and pubescent with depressions anteriorly between eyes. Outline of pronotum and elytra with short, dark and curved setae. Pronotum usually with two longitudinal ridges parallel to the lateral margins, the inner one may be variously obliterated, and traces of others along basal margin. In extreme cases the whole pronotum is lined with a series of ridges. Elytra with strongly punctate striae. Each elytron with a transverse pattern of dense light pubescence at centre. Other patches of pubescence are often present, either humeral or variously on the pronotum. Legs red, last joint of tarsi as long as the rest combined.

Description from 5 Watford specimens at X40

We have been lucky in obtaining adults from the fungus in sealed plastic bags kept in a cool shed. Fungus collected during April 2007 from Whippendell wood.