Megatoma undata (Linnaeus, 1758)
This very widespread species occurs more or less throughout the entire Palaearctic region, reaching north into the UK and far beyond the Arctic Circle in Scandinavia, here it is locally common in the south of England and the midlands, extending north to south Yorkshire but absent from the West Country and most of Wales. Typical habitats are established woodland, parkland and wooded borders on heaths and commons where adults occur under dry and loose bark on decaying deciduous trees and stumps, or more rarely on conifers, among accumulated wood and in spider webs in hollows, within subcortical burrows of other wood-boring beetles or among detritus in avian nests but they have also been recorded from the nests of solitary bees, in old bee hives and nest-boxes, on the ground around Rabbit burrows and are occasionally recorded on the walls of old timber-framed houses. Adults may be seen at night on old dry trees and are sometimes attracted to sap but they are also diurnal and bask on trunks and fence posts in hot sun, at which time they move quickly and fly readily when disturbed, and they may be very difficult to spot in deep bark crevices on oak or where their colour and pattern are cryptic against birch bark. Adults occur during spring and early summer, at which time they may visit flowers and blossom, and mating occurs early in the season. Eggs are laid in subcortical burrows or in the nests of solitary bees and other hymenopterans where the larvae will develop feeding on the remains of insects, shed larval skins and faecal pellets and probably also on pollen, these will produce new generation adults later in the summer, some of which will probably mate and oviposit as both larvae and adults are known to overwinter. Larvae have been recorded from nests of Osmia rufa (Linnaeus, 1758) and have been observed consuming eggs and pupae of Lymantria dispar (Linnaeus, 1758) in continental oak forests, they will also feed on other material of animal origin e.g. adults are occasionally associated with buildings and may oviposit among stored articles such as woollen and leather clothing and they have been recorded consuming specimens in old insect collections. Adults feed almost exclusively on pollen although both adults and larvae have been recorded from various cerambycid burrows and adults have been associated with the spider Salticus scenicus (Clerck, 1757).
Adults should be obvious from the entirely dark colour and bands of pale pubescence to the elytra. 3.5-5.9mm. Head flat above, strongly and densely punctured with a single ocellus which appears as a pale spot on the vertex, eyes strongly convex and prominent anterior to curved temples, antennae 11-segmented with an elongate and sexually dimorphic 3-segmented club; in the male much expanded with the terminal segment about 3X longer than wide, in the female about as long as wide. Pronotum transverse, widest just before the base and narrowed to a rounded anterior margin, surface densely punctured and with scattered pale pubescence which is usually dense near the posterior angles and near the middle of the basal margin. Evenly convex or weakly impressed laterally, posterior angles sharply acute and basal margin strongly bisinuate. Elytra elongate and parallel-sided in the male, less elongate ad slightly dilated towards the apex in the female, densely punctured and with scattered pale scales throughout, and usually with two undulating transverse bands of pale scales, one before the middle and one before the apex. Legs long and slender; femora and tibiae simple, without teeth or rows of stiff setae on the outer margins. Tarsi generally pale compared to the tibiae, 5-segmented and simple, claws small, weakly curved and with a small basal tooth.