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Rhagium mordax (De Geer, 1775)







POLYPHAGA Emery, 1886

CHRYSOMELOIDEA Latreille, 1802

CERAMBYCIDAE Latreille, 1802

LEPTURINAE Latreille, 1802

RHAGIINI Kirby, 1837

RHAGIUM Fabricius, 1775

This species is generally distributed and for most part very common throughout Europe except for the far north of Fennoscandia, to the south it is present along the entire northern Mediterranean and Black sea borders and to the east extends through Asia Minor and Russia to Mongolia and eastern Siberia. In the UK it is common throughout England and Wales although rather less so in East Anglia, and more local and scattered to the far north of Scotland, it is present on the Isle of Wight and Anglesey though absent from Man and most of the Scottish Islands. Typical habitats are woodland and wooded parkland, adults occur from April or May and are usually present into July or August, they frequently visit open-structured flowers such as Hawthorn, Elder and various umbellifers on wooded margins or hedgerows and may also be found basking on trunks and walls etc. Mating occurs early in the year and pairs may sometimes be seen on flowers, the species is widely polyphagous and females will oviposit on a range of dying and decaying deciduous and broadleaf trees e.g. oak, chestnut, alder, birch, beech, ash, lime, hornbeam, pine and spruce among many others, standing as well as fallen timer and old stumps are chosen and eggs are laid among crevices and cracks in the bark, usually in areas where the wood has started to decay and become soft. Larvae develop through the summer forming shallow galleries under the bark and rarely entering the xylem, development usually takes two years though in unfavourable condition can be extended to three years, they are said to be very active and will attempt to bite if handled. Pupation occurs beneath the bark in August or September and for this the larva prepares an intricate oval cell of wood fibres around a depression in the xylem, this stage is brief and adults eclose in the autumn, they soon become hardened and pigmented but they remain in the cell to overwinter and emerge the following spring. The hymenopteran, Ischnoceros sapporensis Gravenhorst, 1829 (Ichneumonidae, Xoridinae) is a small wasp that parasitizes a range of longhorn beetle larvae including those of the present species.

Rhagium mordax 1

Rhagium mordax 1

Rhagium mordax 2

Rhagium mordax 2

Adults vary greatly in size, from 13 to 22mm, and the width of the transverse pale elytral bands can vary to the extent that they merge, moreover the antennae are rather short for members of the family but the species is usually readily identified by overall appearance. Dorsal surface black with irregular dense greyish-brown to pale brown pubescence giving a mottled appearance, each elytron with two black maculae; the median well-defined and bordered by transverse bands of brown or reddish-brown pubescence, and the posterior variously obscured by pubescence. Head quadrate or nearly so, vertex medially impressed and densely punctured, eyes transverse-oval and convex but not prominent, temples longer than the eyes from above and usually devoid of scales, parallel and strongly constricted to a short neck. Pronotum smoothly convex, laterally produced into a strong sharp tooth and constricted before the anterior margin which is curved and narrower than the straight basal margin. Elytra much broader across the base than the prothorax, with broadly rounded shoulders and straight lateral margins that narrow to a continually-rounded apex, each with two fine longitudinal keels and strong and rather dense punctures.

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