Falsoxanthalia desmarestii Latreille, 1807

More generally included in the genus Tetratoma Fabricius, 1790 (subgenus Falsoxanthalia Pic, 1934), this is a widespread European species which extends from Spain to Greece in the south and north to the UK and southernmost provinces of Sweden in the north although it is absent from most of the Baltic countries and very rare across central Europe. The UK distribution includes south east and central England north to Nottingham; there are a few records further north and from Wales but it is absent from the West Country and very local and rare throughout, being most frequently recorded from the home counties. Typical habitats are long-established deciduous woodland and wooded parkland with a good proportion of older trees in various stages of decay, the nocturnal adults occur later in the summer and are active through the winter when they may be beaten from branches infested with various fungi. Adults have been associated with the following species of fungi: Peniophora quercina (Pers.) Cooke, 1879, Laetiporus sulphureus (Bull.) Murrill (1920), species of Stereum Hill ex Pers. (1794) including S. hirsutum (Willd.) Pers. (1800) and, in northern Europe, Corticium quercicola Jülich, 1982, and generally where these occur on lower shaded branches of old oaks. Little is known of the biology but larvae develop within fruiting bodies or among fungus infested wood, they probably pupate in the ground as larvae and pupae have been found among moss growing beneath oak trees, and adults probably eclose in late summer and autumn. Adults may be recorded by taking samples of fungus from decaying oak branches for extraction or by sieving suitable material through the winter.

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​3.5-4.2mm. Elongate and parallel-sided, entirely shiny dark brown to black with a greenish metallic reflection, underside dark brown, legs pale brown, antennae pale with the club darkened, dorsal of body surface finely and densely punctured throughout and with fine pale recumbent pubescence. Head broadest across large convex eyes, evenly convex above and produced anteriorly between lateral antennal insertions, basal antennomere longer and much broader then 2-5, 6 and 7 short and transverse, and 8-11 enlarged to form a long and loose club. Pronotum transverse, broadest in front of distinct posterior angles and narrowed to rounded anterior angles, surface evenly convex but for two well-impressed basal fovea, lateral margins smooth and narrowly explanate. Elytra with rounded shoulders, near-parallel for the basal two-thirds and smoothly curved to a near-continuous apical margin, without striae or distinct impressions, punctures stronger and denser in the basal half, becoming finer and so appearing more widely spaced towards the apex. Legs long and slender, the tibiae straight and only weakly broadened from the base to truncate apices, each with very short and fine terminal spurs which are easily overlooked. Tarsi 5-5-4, the basal segments weakly lobed ventrally, claws smooth and without a basal tooth.