Triplax lacordairii Crotch, 1870
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POLYPHAGA Emery, 1886
CUCUJOIDEA Latreille, 1802
EROTYLINAE Latreille, 1802
TRITOMINI Curtis, 1834
Triplax Herbst, 1793
This is a rare and very local species of warm deciduous forests in Western and South Western Europe and North West Africa, it is otherwise known from a few sites in France, Italy, Austria and Slovakia, and a single site in Germany (Nymphenburger Schlosspark), it is absent from Denmark and the Baltic countries but occurs very locally in a few sites in Central and Southern England. Despite the species rarity, and it is probably declining in the UK, it is usually common where it occurs, adults have been recorded an all months from May until September, peaking in abundance during June and again in late summer, they are nocturnal and associated with macro basidiomycete sporocarps on a range of broadleaf trees but, at least in the UK, especially birches (Betula L.) and oaks (Quercus L.) Adults have been recorded from decaying sporocarps of Cerioporus squamosus (Huds.) Quélet (1886) and Fomes fomentarius (L.) Fr. 1849 in Spain, and from Oyster fungus (Pleurotus ostreatus (Jacq.) P. Kumm. 1871 in the UK, but as is typical of much of the genus and certainly of our common UK species, they probably occur on other fungi such as Inonotus P. Karst (1879), Laetiporus Murr. (1904), Piptoporus P. Karst (1787) and Stereum Hill ex Pers. (1800). Both adults and larvae feed on fruiting bodies, larvae develop within fungi through the summer, usually in groups and usually alongside other those of other mycetophagous beetles and flies, and are thought to remain within or drop to the ground to pupate in late summer or autumn, which is again typical of the genus. It is likely that adults are fully formed in the autumn but remain in situ until the spring as they have been found through the year in France. Adults remain under bark or within host material during the day and become active in the evening when they may be seen in numbers on fungi and decaying wood although they need to be looked for carefully as several members of the genus often occur together. Sieving or beating likely material over a sheet is the best sampling method.
3.0-4.2 mm. Elongate-oval and moderately convex, head and pronotum reddish-brown or orange, in rare cases the head is dark reddish, elytra black, sometimes with a faint metallic blue reflection, antennae pale with the club at least in part darkened, legs orange. Head evenly convex and finely punctured between convex and prominent eyes, temples long and weakly converging and clypeus narrowed anteriorly from the lateral antennal insertions. Terminal maxillary palpomere widely securiform, and antennal club 3-segmented, long and loose. Pronotum transverse, broadest at or near the base and narrowed to slightly protruding anterior angles, posterior angles sharp and almost perpendicular and the basal margin bordered and widely sinuate, surface evenly convex, finely and sparsely punctured and without sculpture but for weak basal fovea. Scutellum dark, as the surrounding elytra. Elytra elongate and gently narrowed from sharp humeral angles to a continuous apical margin, basal margin finely crenulate, striae punctured but hardly impressed, and interstices flat. Abdomen, meso- and metasternum black. Legs robust and moderately long, femora unarmed and tibiae flattened and moderately expanded from the base to truncate apices. Tarsi 5-segmented, segments 1-3 expanded or bilobed, segment 4 diminutive (and so they often appear 4-segmented) and the terminal segment long and slightly curved. Claws smooth and without a distinct basal tooth.