Xylotrechus rusticus (Linnaeus, 1758)
This is among the most widespread of the Palaearctic longhorns; it occurs continuously from Portugal to the far east of Russia, China, Japan and Korea and is widespread in the Oriental region, it is present throughout Asia Minor and North Africa and extends north above the Arctic Circle in Fennoscandia and Russia but is absent from the UK; it is included on this website as a specimen was found alive by the author in a warehouse in South Hertfordshire in Feb 2019 and since that time several other specimens have been reported although these may have been Hylotrupes bajulus (Linnaeus, 1759) which we have also found at the same site. The species is locally common across Europe although less so in the west and occurs in a wide range of habitats; typically deciduous or mixed woodland but they also visit trees in parks and gardens, they will often bask on bark exposed to the sun and may be common in warm and open wooded areas in the south, but they have a wide temperature tolerance and at high latitudes all life stages can survive prolonged freezing. Across Central Europe they occur from May until July, peaking in abundance in June, they are diurnal and generally very active; from experience they run fast and erratically, superficially resembling a tiger beetle as they move, they are very cryptic on bark and fly well but do not visit flowers. The species is widely polyphagous on broadleaved trees, especially on poplars (Populus L.); they breed in freshly dead or fallen trunks and branches although in China, where it has become a very serious pest since the 1970s and outbreaks have destroyed or weakened thousands of hectares of woodland , it mostly attacks living trees and almost always species of Poplar. As such the species is considered a threat to woodland in many areas and monitoring has revealed several specimens at ports in the United States. Breeding occurs in June and July and females may fly for prolonged periods in search of suitable host material, they choose dry wood on dead or dying standing or fallen trees and lay eggs into exposed and cracked timber and will often visit several sites to do so. Larvae burrow deep into the host wood and are known to complete their development after overwintering as final instars but they have also been known to overwinter for a second or third time depending on local conditions, they resume feeding deep in their tunnels in late winter or early spring but move to the surface when ready to pupate. Pupation occurs in the spring in a chamber constructed under thick bark or near the surface within the larval borings, adults eclose soon afterwards but remain inactive until at least mid-May when they tend to emerge in numbers. Given the species tolerance to a wide range of conditions, and given that several specimens have been reported to me from the same site in North Watford, it seems very likely that further specimens will be reported in the UK.
9.0-20.0 mm. Elongate and discontinuous in outline, with very long legs and short antennae, colour varies from pale brown to dark grey, the pale elytral markings are also variable but the arcuate subapical band coupled with the form of the pronotum will identify this species. Head hypognathous with weakly convex and emarginate eyes, usually black with various pale grey or brown symmetrical markings on the vertex and frons, antennae reaching back beyond the base of the meso-femora in the male, in the female extending just beyond the pronotum but not reaching the base of the meso-femora. Pronotum transverse and convex, broadest behind the middle where there is often a distinct angle and narrowed to obtuse angles, anterior margin curved, basal margin straight, surface densely punctured throughout, usually brown or grey with a variously formed longitudinal band of pale scales either side of the disc and the lateral margins extensively scaled. The mesonotum is often narrowly visible from above and here there is a small patch of pale scales either side of the middle just behind the scutellum. Elytra broadest at sloping shoulders and gradually narrowed to separately rounded apical margins which cover the abdomen in the male but leave the pygidium exposed in the female, surface finely and densely punctured throughout, usually with scattered pale scales and three transverse bands; one in the basal third which may be fragmentary, one about the middle which usually extends forward along the sutural margin, and one at the apical third which is very characteristically-shaped and reaches, or almost reaches the lateral margin, the apex is usually filled with pale scales and these may extend along the suture to meet the subapical band, in some specimens the markings may be worn or vague due to rather dense background scales but the pattern is usually discernable. Legs long and slender; all femora clavate, tibiae only weakly thickened from the base and with strong apical spurs. Tarsi 5-segmentes, basal segments of front tarsi expanded in both sexes, basal segment of middle and, especially, hind tarsi very long, third segment of middle and hind tarsi narrowly bilobed.