Lithostygnus serripennis Broun, 1914

Thought to be native to the Australasian region, where it is known from New Zealand to New Guinea, this species has long been established in Europe and while the distribution remains restricted it seems to be slowly expanding; so far it is known from the UK, Germany and The Netherlands and there are records from North Africa. In the UK it is widespread and locally common across south-eastern and central England and Wales, very local and scarce further north and there are records from Man, Ireland and Orkney.  Here the species is usually synanthropic, occurring on mouldy walls, old woodwork etc in damp situations and, especially, among stored products or packaging material in cellars and out-houses, but specimens often occur in the wild among mouldy wood and decaying vegetation, especially among leaf-litter under old oak trees. Adults have been recorded year-round but they are mostly recorded through the summer, they are nocturnal and rather secretive and, because they are flightless, are probably under-recorded. Both adults and larvae feed on spores and mycelia, under artificial conditions they probably breed throughout the year as large populations may occur at any time, but in the wild the life-cycle is unknown. Sampling is easiest by searching suitable artificial sites but adults sometimes appear among extraction samples of decaying wood etc. or in samples sieved from litter or old straw etc. but they are tiny and will need to be looked for very carefully.

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​1.3-1.4 mm. Elongate and discontinuous in outline, glabrous, entirely dark to pale brown and usually with traces if pale secretions on the underside. Distinguished among our fauna by the head structure and fused elytra. Head slightly transverse and broadest across small, convex eyes temples short and strongly converging, cheeks bordered, long and converging, labrum widely transverse and weakly rounded anteriorly.  Head surface uneven, with a fine oblique ridge from each eye, these almost converge but angle forward to run parallel to the clypeal margin. Antennae 11-segmented with two enlarged basal segments and a two-segmented club. Pronotum transverse, broadest in front of the middle and narrowed to slightly-oblique posterior angles, anterior angles widely-produced and apical margin curved forward.  Lateral margins variably, though usually distinctly, denticulate, surface uneven, convex across the disc and widely explanate laterally, disc with two transverse keels, or at least distinct series of small tubercles. Front coxae separated by a distinct process. Elytra evenly curved laterally from rounded shoulders to an accuminate apical margin, lateral margin denticulate although these become weak towards the apex, each with six longitudinal rows of wide punctures that may become confused in places, especially laterally, interstices narrower than the puncture rows, the third and fifth keeled almost to the apex. Legs long and narrow with all femora and tibiae about equal in size. Tibiae without external teeth, spines or terminal spurs. Tarsi 3-segmented in both sexes, basal segments lobed but narrow, and the terminal segment long and curved. Claws smooth and not, or only obscurely, toothed at the base.