Rhagium bifasciatum Fabricius, 1775
POLYPHAGA Emery, 1886
CHRYSOMELOIDEA Latreille, 1802
LEPTURINAE Latreille, 1802
RHAGIINI Kirby, 1837
RHAGIUM Fabricius, 1775
This is one of most common European members of the family, it occurs throughout southern and central Europe north to the UK and the south of Fennoscandia but is absent from some areas of the northeast and some of the Mediterranean islands, to the east it extends through the Caucasus and Asia Minor into western Russia. Here it is locally common to the far north of Scotland including Anglesey and the Inner Hebrides but is absent from Man, it is also widespread in the north and east of Ireland. The typical habitat is damp deciduous, coniferous or mixed woodland with plenty of timber in various stages of decay although populations may also occur in isolated trees or fallen timber on moorland etc. Adults occur from April until June or July and will often be found in numbers, especially in early spring when they are just beginning to emerge from their overwintering sites under bark, they fly well and visit a range of flowers to feed on pollen, especially those of elder, hawthorn and various umbels, and they are also known to feed on pine needles. Mating and oviposition occurs in the spring and a wide range of both broadleaf and coniferous trees have been recorded as hosts e.g. pine, spruce, larch, fir, chestnut, oak, birch, beech. Ash, hornbeam, alder, poplar, hazel, hawthorn and hazel etc., mating pairs may be observed during the day on bark or flowers and females lay eggs in batches among damp bark on stumps, and fallen and standing trunks. Young larvae bore galleries beneath bark but as they grow they penetrate the xylem, producing long meandering tunnels loosely packed with wood dust and frass, they usually develop over two years but this may be extended to four or five years depending upon the temperature and humidity. Pupation occurs in late summer or autumn in a cell beneath the bark or, if the wood is very soft, within a cell constructed parallel to the grain deeper in the xylem, adults eclose during September or October and are soon fully formed but they remain in the pupal cell until the following spring when they will emerge en masse.
Adults vary in size from 12 to 22mm but are readily identified by the elytral markings; dark across the base and brown to the apex, with an oblique yellow band in the basal half and a transverse, usually curved, band in the apical half, these may be reduced or enlarged, in extreme cases they may be wide and merge across the centre, this variation is continuous but a long list of varieties have been named. Forebody, antennal scape and femora black, remainder of the antennae and legs variously brown. Head with weakly convex, transverse eyes and long, near-parallel temples that curve to a wide neck, vertex longitudinally impressed and antennae long and slender, overlapping the elytral base at rest. Pronotum with fine golden pubescence but for a smooth median line, lateral margin with a large and sharp tooth about the middle, anterior and posterior angles distinct and the basal margin bordered and bisinuate. Scutellum with dense pale or golden pubescence. Elytra with broad rounded shoulders and tapering to separately rounded apical margins, strongly and rugosely punctured across the base and rugose towards the apex, each with two shiny longitudinal keels that terminate before the apex. Colour variable but the shoulders, lateral margins, between the yellow bands and apically pale brown and the sutural area extensively darker.