Diaperis boleti (Linnaeus, 1758)
This widespread and locally common species occurs sporadically throughout Europe except in far northern areas, extending to northwest Africa, the Middle East and through Siberia to the far east of Asia; in the UK it was formerly very rare and local but has expanded its range and become generally common throughout the southeast in recent decades. The typical habitat is old established broadleaf woodland with plenty of trees in various stages of decay but it may also occur on isolated old trees in parkland or gardens etc. Adults are nocturnal and generally occur on various host fungi, particularly Laetiporus sulphureus Piptoporus betulinus but also Fomitopsis pinicola, Fomes fomentarius and Polyporus squamosus, they feed on the fruiting bodies and may be detected by the large tunnels they leave as they do so. The entire life cycle occurs on the host; adults mate in the spring and eggs are laid in the fungal tissue, larvae quickly emerge and feed on the host; they are pale and cylindrical with well developed legs and a dark head with prominent mandibles, development is rapid and when fully grown they construct a pupal cell within the host and new generation adults occur from early summer. Oviposition occurs over a long period as we have found teneral adults through the summer, they disperse nocturnally by flight and, as the host may only persist for a single season, new host material must be found each year although they are able to use dry remains of old fruiting bodies and will occur among dead wood and loose bark long after the fungus has decayed and vanished. New host material is quickly colonized and adults tend to occur in numbers, sometimes dozens crammed tightly under the fungus and among surrounding bark, and they persist until the host decays or becomes damaged; we even find them among brackets that have been broken and lie around the base of stumps etc. There is a single generation each year, adults overwinter among bark or dead fungi and occur regularly among extracted samples but the easiest way to record them is at night by torchlight when they are active on the host.
Adults are quite distinct by virtue of the size and colour, they might be mistaken for a coccinellid or a chrysomelid but the tarsi are distinct in both cases. 7-8mm. Form short oval and very convex, entirely shiny black with 2 transverse pale bands to each elytron; yellow in teneral specimens darkening to red when mature. Head transverse with a deep impression between the eyes, eyes large and emarginate anteriorly, vertex strongly punctured and with fine, indistinct granular microsculpture. Antennae black, from segment 4 widely transverse, terminal segment rounded. Pronotum transverse; widest at the base and roundly narrowed to distinct anterior angles, surface convex and finely punctured. Elytra elongate with distinct humeral angles and continuously rounded apically, black with 2 transverse bands and the apical area pale, striae distinct and regularly punctured, interstices flat and finely punctured. Legs long and robust; black with fine yellow pubescence, all tibiae with 2 longitudinal and finely dentate ridges. Tarsi 5-5-4, without distinctly lobed segments, terminal segment long and curved, claws long and curved, smooth and without a basal tooth.