Pissodes castaneus (De Geer, 1775)
A Palaearctic-wide native also established in Asia Minor and North Africa, this species is regularly intercepted in the United States and has become established in several South American countries e.g. Brazil. Argentina and Chile (although some of these are thought to be misidentified specimens of P. radiatae Hopkins, 1911, a Nearctic species) and there are occasional records from imported timber around the world. The distribution includes almost the whole of Europe north to the UK and some central provinces of Sweden and Finland, it is present on most of the Mediterranean and Atlantic islands and it extends to the tree line in mountain areas. In the UK it is locally common across southeast England, mostly coastal in Wales and sporadic and generally infrequent further north to the Scottish Highlands. Typical habitats are coniferous and mixed woodland but adults are strong fliers and long-lived and during spring and summer dispersals may occur on trees in wooded parkland or even gardens, they naturally occur in small numbers but females are very fecund and so where suitable host trees are grown commercially very large and damaging populations can build up. Host trees include most species of pine (Pinus L.) but more especially Scots pine (P. sylvestris L.) and Black pine (P. nigra Arnold, J.F.) as well as other conifers including Yew (Taxus baccata L.), European Larch (Larix decidua Mill), Silver Fir (Abies alba Mill), Nordmann Fir (A. nordmanniana (St.) Spach) and Norway spruce (Picea abies (L.) H. Karst.) Adults overwinter under bark etc. and become active in the spring; during April in warmer parts of Europe but usually not until May in the north, they disperse by flight and are mostly nocturnal, they may be found under bark or within bark crevices during the day although on the warmest days are often active on trunks and logs. Feeding, mating and oviposition occur throughout the season; both sexes feed on bark, small shoots and buds and females bore through young bark to oviposit. Small groups of eggs are laid into puncture-wounds, on saplings usually between the root collar and the first branches and in older trees low down in trunks and branches, females are very fecund and under artificial conditions have laid more than 500 eggs over their lifetime.
Pissodes castaneus 1
Pissodes castaneus 2
Larvae emerge after a week or so and bore into the phloem where they feed on sap, they produce long galleries that radiate characteristically when larger groups of eggs are laid, they pass through four instars and usually do not diapause. All larval stages have been found to overwinter and pupae occur throughout the year. In temperate regions there is one generation each year but in warmer southern areas there may be two or two generations may overlap, in colder northern regions each generation usually develops over two years. Adults may be found by day or night by searching among bark crevices or under loose bark but in the warmest weather they may bask in the sun or take flight.
5.5-7.0 mm. Elongate and more or less continuous in outline, entirely reddish-brown, often with the appendages and rostrum a little paler, pronotum and elytra with characteristic patches of pale and yellowish scales. Head with widely diverging temples and weakly convex eyes that form the outline and meet the base of the rostrum, surface finely and moderately densely punctured, rostrum long, weakly curved and distinctly expanded towards the apex, scrobes placed laterally and not visible from above. Antennae inserted about the middle in females and in front of the middle in males, scape gradually thickened from the middle, funiculus gradually broadened and so the club is not always distinct. Pronotum quadrate or weakly transverse, broadest in the basal half and narrowed to a distinct subapical constriction and narrow apical margin, in the basal half not, or only slightly, narrowed before almost perpendicular posterior angles. Basal margin bisinuate either side of the middle, pronotal surface strongly and closely punctured, confluently so in places, the cuticle between smooth and shiny, each with scale, most of which are inconspicuous but some are larger (typically two spots on the disc and an indistinct pattern near the posterior angles) and form a pattern. Lateral prosternal margins, metepisterna and metasternal margins with conspicuous elongate (at most 1.5X longer than wide) white scales. Elytra almost parallel-sided from rounded shoulders to a weak subapical constriction and separately-rounded apical margins, surface shiny and uneven, especially in the basal half, striae strongly punctured and complete to the apex, interstices broader than the striae, in the basal half often with transverse ‘ripples’, with tiny pale scales throughout and two transverse series of larger pale and yellow scales, one before and one after the middle. Legs long and robust, femora without a ventral tooth, tibiae sinuate internally and each with a sharp incurved tooth which is continuous with the external margin. Tarsi pseudotetramerous, claws smooth and free.