Phymatodes testaceus (Linnaeus, 1758)

Tanbark Borer

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POLYPHAGA Emery, 1886

CHRYSOMELOIDEA Latreille, 1802

CERAMBYCIDAE Latreille, 1802

CERAMBYCINAE Latreille, 1802

CALLIDIINI Kirby, 1837

PHYMATODES Mulsant, 1839

This native Palaearctic species is generally common throughout Europe from North Africa to Southern Scandinavia and the U.K. and from Portugal east through Asia Minor, Israel, Syria and Northern Iran to the far east of Russia and Japan, and following introductions it has also become established in the United States and Canada where it is widespread in temperate latitudes. Here it is generally common across England and Wales north to Nottingham and there are scattered records further north to the Scottish borders. The typical habitat is broadleaf and mixed woodland, parkland and gardens with plenty of damaged and fallen timber and logs but the beetles are rarely seen as they are crepuscular and nocturnal, often coming to light or sap runs on trunks. Adults tend to be very active and will run rapidly or fly readily when captured or exposed from under bark etc. during the day. They are active from May to July or later, depending on the year, and may be found under bark in the pupal chamber earlier in the year. Hosts include various broadleaved trees e.g. Fagus, Prunus, Fraxinus, Salix and Castanea but Quercus seems to be preferred and they have also been recorded from several conifer genera e.g. Tsuga and Picea (both Pinaceae). Small and pale eggs, about a millimetre long, are laid under bark or in crevices of standing or fallen timber or logs and the larvae initially tunnel beneath the bark leaving galleries densely packed with frass, in large infestations the bark may become loose with dense masses of galleries beneath. Larger larvae bore into the xylem and produce surface galleries, they may measure 18mm when fully grown, and pupation occurs in the spring; a pupal cell is constructed beneath the bark in the outer xylem and adults eclose after about 3 weeks but remain in the cell until April or May when they emerge through circular holes bored through the bark. In southern European latitudes the life cycle is complete within a year but further north it is generally completed over three years. They have formerly been pests of considerable economic importance as the sapwood of oak trunks and branches may be completely destroyed, effectively ‘ringing’ the tree and causing its death.

8-16mm and widely polychromatic, typically entirely testaceous but variable through red to a deep blue black, a common form has the pronotum red and the elytra blue. Head distinctly narrower than the pronotum; strongly deflexed in front of prominent antennal tubercles and with a longitudinal impression between the eyes; finely punctured and pubescent throughout. The terminal segment of the palps is securiform, the antennae entirely testaceous and extending back beyond the elytral apices; the third antennomere about equal in length to the fourth. Distance between the antennal insertions greater than the narrowest distance between the eyes. Pronotum transverse; angled laterally behind the middle where it is broadest and lacking a border, the surface finely punctured and pubescent and with a raised longitudinal ridge at the base. Elytra broadest behind prominent shoulders then parallel or nearly so to weakly divergent and separately rounded apices, the surface finely and sparsely punctured and with sparse recumbent pubescence. The elytral colour varies but is only very rarely metallic and generally has a translucent appearance with the hind wings sometimes visible. The abdomen often protrudes beyond the elytral apices. The legs are long and slender, the colour is very variable but in pale specimens it is usually testaceous, the tibiae are at least as long as the expanded femora and the terminal meta-tarsomere is as long as the remainder combined. This species might be mistaken for a Cantharid (especially Cantharis livida) or the Oedemerid Nacerdes but the form of the head and the tarsal formula are distinctive.

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