Endomychus coccineus (Linnaeus, 1758)
This widely distributed and generally common species occurs from Spain eastwards to Central Asia and from Italy north to Scandinavia. In the U.K. it is locally common throughout England and Wales, and there are a few records scattered through Scotland north to Inverness. Adults occur year-round, during the winter they may be found beneath damaged and loose bark on a range of broadleaf trees; lime, horse chestnut, beech, poplars, oak, willows and birch, often aggregating in small groups. They are nocturnal and become active in early spring, from then until the autumn they are easily observed at night in the vicinity of fungus on trees and logs, often among other saproxylic beetles. They may occur wherever suitable host fungi are growing; parks, gardens, wasteland and, especially at least in our South Hertfordshire area, along river margins, they should be searched for on standing or fallen trees with areas of damaged or loose bark and signs of fungal infection. Both adults and larvae are fungivores and both stages are gregarious, in the spring the larvae will generally be found under bark in groups of a dozen or more. Locally we have observed the adults mating in September and October, larvae of all stages in mid-March and pupae under bark in April and May. When startles the adults may begin reflex bleeding, secreting a pale pink haemolymph from the junctions of the femora and tibiae on all legs.
This relatively large, 4-6.5mm aposematic species should be easily recognized by the dorsal colouration; vivid red with 4 elytral spots, a central longitudinal line on the pronotum and the head and appendages black or nearly so although, rarely, the pronotal line may be reduced and the head, in fresh specimens, may be pale. The entire dorsal surface is glabrous and randomly and densely punctured. The head, usually mostly hidden within the pronotum, is slightly elongate with large eyes and long, robust antennae, the insertions of which are separated by about the length of the basal segment. The maxillary palpi are short with the terminal segment securiform. The pronotum is transverse with rounded and produced front angles, acute hind angles and finely bordered lateral margins. The surface is depressed either
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side of a raised discal area. Prosternal process narrow and weakly curved at the apex. Scutellum obvious, triangular and dark as the pronotal stripe or, rarely, pale. Elytra broadly oval; continuous in outline with, and a little broader than, the pronotum, the surface lacking striae. Each with 2 large black spots, the anterior a little larger, and finely bordered lateral margins. Legs robust and pubescent, the femora broader than the tibiae, all tibiae broadened towards the apex and lacking terminal spines. Tarsi 4-4-4; segments 1 and 2 bilobed, 2 widely so, 3 very small and 4 elongate and broadened towards the apex. Claws smooth and not toothed at the base.
ENDOMYCHUS PANZER, 1795
Endomychus is a Holarctic genus of about 40 species with the greatest diversity in the Oriental region; China, India, Vietnam, Laos etc. and with several species known from New Zealand. Only 2 species occur in North America; E. limbatus (Horn, 1870) and E. biguttatus Say, 1824. So far as is known all species are fungivores, the adults feeding on fruiting bodies while the larvae feed on mycelia of Basidiomycetes. At least some are known to be oligophagous e.g. E. biguttatus has been recorded feeding on Schizophyllum communae, Auricularia sp. and Piptoporus betulinus. Many species are brightly coloured and patterned, and several are closely similar in this respect e.g. E. armeniacus Motschulsky, 1835 superficially resembles our U.K. species E. coccineus (Linnaeus, 1758), and many species are entirely dark or brilliantly metallic blue or green e.g. the Asian E. gorhami (Lewis, 1874) and E. jureki Mader, 1936.