Ptinomorphus imperialis (Linnaeus, 1767)
POLYPHAGA Emery, 1886
BOSTRICHOIDEA Latreille, 1802
EUCRADINAE LeConte, 1861
HEDOBIINI Mulsant & Rey, 1868
Ptinomorphus Mulsant & Rey, 1868
This species is generally common from lowland to low mountain altitudes throughout Europe, extending east into Ukraine and western Russia and north to the UK and southern provinces of Fennoscandia although it is absent from some of the northern Baltic countries, in the UK it is locally common across England north to Nottingham, though generally absent from the West Country and Wales, and very local and scarce further north to southern Scotland. Adults are active from May until July, they occur in deciduous woodland and wooded parkland with plenty of trees in various stages of decay. Early in the season they visit a variety of flowers where may be observed feeding on pollen and nectar in bright sun; we have swept them from umbels and flowers of Viburnum opulus L. but they have also been recorded from blossom on hawthorn and various fruit trees, later on they are associated with decaying wood on logs, trunks and branches and they often occur among lavish growths of old ivy. Mating occurs early in the season and pairs have been observed on flowers during the day, females oviposit among dead bark on all parts of standing trees, from the crown to the lower trunk, and also in old stumps and fallen branches that still retain their bark. Larvae feed initially under bark but as they grow they bore into the xylem where they will develop until the autumn when they pupate in an oval silky-grey cocoon within the wood, adults have been observed within their cocoons in the autumn but they do not emerge until the spring. Under favourable conditions the life cycle is completed over two years but this may extend up to three years in cooler northern areas. Adults may be swept from flowers and foliage in fine weather, we have also swept them from ivy and cypress trees in local deciduous woodland and found them under bark of old decaying beech and ash, they fly well and so may occasionally occur far from suitable habitats but unlike many saproxylic species they appear not to be active at night.
3.4-5.8mm. Very distinctive among our UK fauna due to the contrasting pattern of grey or creamy and pale recumbent pubescence to the pronotum and elytra; the pale, almost white, pubescence present on the lateral margins of the pronotum, covering the scutellum and forming an oblique stripe from the humerus to the elytral suture and usually joining a subapical transverse band. Head prognathous and oriented obliquely forward, smoothly convex and without impressions, eyes small and only weakly convex, antennae long and filiform with all segments elongate, from above the head is generally hidden beneath the prothorax but can be manipulated forward and largely exposed in set specimens. Pronotum flat anteriorly and strongly raised in the basal half, widest across the base and gradually narrowed to a curved anterior margin, lateral margins without borders and basal margin weakly curved. Scutellum always distinct; broadest across the base and narrowed to a truncate apical margin. Elytra elongate with rounded shoulders, sub-parallel and smoothly rounded to a continuous apical margin, transversely convex and, in lateral view, weakly vaulted from the basal third, roughly and densely punctured throughout and without striae. Legs robust and moderately long, the femora widely visible in normal setting and the tibiae narrow and weakly expanded to truncate apices, each with a tiny spur at the inner apical angle. Tarsi 5-segmented; the basal segment elongate, the rest transverse and lobed, claws smooth, long and gently-curved and lacking a distinct basal tooth.