Mycetophagus populi Fabricius, 1789
This widespread though very local and generally rare species occurs throughout Europe from the Pyrenees to Greece and north to the UK and northern provinces of Fennoscandia, to the east it occurs through Asia Minor, Ukraine and Russia and extends sporadically to eastern parts of Siberia. In the UK it is widespread across the south of England and the midlands though absent in the West Country and known from only a very few records in the south of Wales, it is very infrequently recorded and classified as nationally scarce. Adult occur in open deciduous woodland, wooded parkland and on large solitary trees in grassland areas, they are most frequently recorded during the winter and spring and, on the continent, teneral specimens have been found in September. They usually occur under loose bark and among decaying damp wood in hollows on stumps, standing and fallen trunks and fallen branches and they sometimes appear at sap in the spring. They have been recorded from a wide range of trees including elm (Ulmus L.), poplars (Populus L. including P. tremula L.), willows (Salix L.), alder (Alnus glutinosa (L.) and A. incana L.)), sycamore (Acer pseudoplatinus L.), oak (Quercus L.) and various cultivated fruit trees, and on the continent from Norway spruce (Picea abies (L.)) and among fruiting bodies of Cerioporus squamosus (Huds) Quélet (1886) on fallen branches. Larvae develop through the spring and summer among soft wood infested with fungal mycelia and the species is thought to be univoltine with pupation occurring late in the year and the resulting adults overwintering and reproducing the following spring.
4.0-4.5mm. Distinguished from other members of the genus by the dense and very fine dorsal punctures and pubescence, and the form of the terminal segment of the maxillary palps which is distinctly broader than the penultimate segment. Long-oval with the head much narrower than the pronotum and the pronotum and elytra separately rounded, colour variable but usually pale orange-brown, usually with the head a little darker than the elytra, and with two broad transverse paler bands to each elytron; one across the basal quarter and across the apical third although they vary in size and intensity. In some European specimens the ground colour of the elytra is very dark, almost black and often with a faint metallic blue reflection. Head transverse with asymmetric and very convex eyes and long temples that are usually hidden within the prothorax, antennae 11-segmented and shorter than the width of the pronotum, basal segments narrow compared with segments 8-11 which form a distinct club. Pronotum broadest near the base and narrowed to rounded posterior angles and protruding anterior angles, lateral margins smooth and surface evenly convex with two wide impressions across the base. Elytra with rounded shoulders and weakly broadened to a continuously rounded apical margin, striae impressed and punctured into the apical quarter, interstices weakly convex. Legs entirely pale. Male tarsi 3-4-4. Female tarsi 4-segmented.