Triplax russica Linnaeus, 1758
Widely distributed but local, with records from two distinct regions; south east England and the midlands north to York, and northern Scotland around Moray and Perth. Found in fungal fruiting bodies on trees. Around Watford from mid May onward, not found before this despite extensive sampling. Found throughout our area, usually in small numbers (<5) among large populations of Triplax aenea Schaller and Mycetophagus quadripustulatus L. within the fruiting bodies of fungi around the base of deciduous trees, in our experience Fagus and Aesculus. They are very quick to colonize, appearing within a day or two of the fungus opening.

Black elytra and large size, 4-5.7mm. make this species distinctive but the abdomen should always be examined; here it is red, in the similar T.lacordairei Crotch it is black. Antennae black, sometimes lighter towards base, 11 segmented with a three segmented club. Head red, darker than pronotum, finely punctate with transverse suture behind eyes. Pronotum red, finely punctate and bordered laterally and basally. Front margin produced. Elytra entire, distinctly bordered, with faintly impressed punctate striae, sometimes obscure on disc. Fifth stria deeply impressed at shoulder with distinct, wrinkled basal stria from scutellum to humeral angle. Legs entirely red. Tarsal segments 1-4 broad, 5 elongate.

Description from 3 Watford specimens at X20

Particularly Inonotus hispidus on Fraxinus in the west, preferring Fomes fomentarius on Betula in the south. (Alexander).