Dryophthorus corticalis (Paykull, 1792)
This widespread species occurs throughout Europe north to southern Scandinavia and extends east through Siberia to the far east of Russia, Japan and South Korea, it also occurs in North Africa and has been recorded from the Nearctic region. In the UK it was first recorded in July 1925 at Windsor Forest and has been recorded regularly since that time, this remained the only locality until recently when it was found at nearby Richmond Park (Surrey), Langley Park (Buckinghamshire) and during a survey of saproxylic invertebrates survey at the National Trust’s Croome Court near Worcester. Scattered postglacial records from the Somerset Levels to Yorkshire show that it was formerly much more widespread in the south. On the continent it occurs among decaying wood of a range of broadleaf and coniferous trees, often alongside the tree ant (Lasius brunneus (Latreille, 1798)) although whether there is a specific association is not known, and usually in mature trees in forest areas. Here it has been found throughout the year among red-rotten heartwood of old oak trees, usually in ancient woodland and where the tree ant is present, and in flight-interception traps during June and July which may be the usual period of dispersal. The larva is thought to feed on dead wood but beyond this little is known of the beetle’s biology. Despite its wide European distribution the species is generally very local and considered to be rare e.g. in Germany and the UK it is classed as endangered and in Denmark critically so, but the general lack of records may be at least partly due to its cryptic lifestyle and the lack of appropriate sampling.
Until recently Dryophthorus was included in the curculionid tribe Cossonini Schönherr, 1825 but is obviously distinct in having, among the general features of the present family, five-segmented tarsi and four-segmented antennal funiculus. Adults are very distinctive among our fauna and should not be confused with any other species. 2.6-3.3mm. Elongate and discontinuous in outline and entirely dark brown to black although in pictures specimens often appear patchy due to encrusted wood dust etc. Head convex, broadest at the base with long temples narrowed to small and flat eyes, vertex with wide and flat punctures, rostrum broad, elongate and dilated in front of the antennal insertions. Antennae inserted within the basal third of the rostrum, scape short and evenly broadened from base to apex, funiculus with four transverse segments. Pronotum quadrate or slightly elongate, narrower than the elytra and strongly constricted before the apex, the surface with very wide and flat punctures. Elytra with sloping shoulders, curved and narrowed laterally to separately rounded apices, apical area produced by the fused fifth and seventh interstices. Striae with evenly-spaced wide and shallow punctures, interstices raised into flat ridges which are finely punctured. Legs long and robust; fore-femora broad and curved, without teeth, mid- and hind femora longer and narrower, tibiae narrow, straight and without teeth; the fore-tibiae produced apically into a curved and sharp process. Tarsi 5-segmented but appearing 4-segmented due to the tiny fourth segment. The sexes are difficult to separate but by comparison the male has slightly shorter and broader rostrum and the antennae are further from the head, about a third the rostral length.