Curculio venosus (Gravenhorst, 1807)
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POLYPHAGA Emery, 1886
CURCULIONOIDEA Latreille, 1802
CURCULIONINI Latreille, 1802
This widespread western Palaearctic species extends from Spain to Western Russia and north to the UK and southern provinces of Fennoscandia, it is also known from Algeria, Morocco and throughout Asia Minor, it is generally common in southern and central areas but more sporadic and local in the north. In the UK it is locally common across England and Wales north to south Yorkshire though less so in the West Country and more prevalent in certain areas e.g. Easy Anglia, the central midlands and the south east below London. Typical habitats are deciduous and mixed woodland and wooded parkland with plenty of oak but they also occur on individual trees in hedgerows and gardens etc, adults are active over a long season from April until October but may occasionally occur through the winter. Host plants include various oaks; in the UK usually on Pedunculate oak, Quercus robur L., but more widely on Portuguese oak, Q. faginea Lam., Sessile oak, Q. petraea (Matt.), Downy oak, Q. pubescens Willd., Evergreen oak, Q. ilex L. and Pyrenean oak, Q. pyrenaica Willd, and various cultivars etc. Breeding occurs in spring and early summer and females oviposit inside undeveloped acorns, first using their long rostrum to penetrate the soft shell and then inserting their long ovipositor to lat one or, more usually two eggs. Larvae develop within, feeding upon the contents until they are fully-grown in late summer or autumn, they leave the acorn after it falls to the ground and they overwinter in the soil. Most overwintered larvae will pupate in the spring to produce adults from April but a proportion will diapause and remain in the soil for a further year or even two years before they pupate, and it is thought that some larvae remain within the fallen acorns and diapause within for an extra year or two. Adults feed on foliage and spend most of their time on twigs and leaves, they are therefore easily sampled by beating or sweeping, and although they seem to be primarily diurnal they are often common at light traps in wooded areas; they fly down from trees and usually remain on the ground in the shade of the trap but will occasionally fly directly into the light.
5.9-9.0 mm. An elongate species with a large pronotum and strongly tapering elytra, pronotum extensively dark brown, usually with a central and lateral paler longitudinal stripe, elytra pale brown with two or three transverse bands of darker scales, legs with pale scales throughout, antennae dark brown. Head transverse with convex eyes continuous with the outline and short diverging temples, surface evenly convex and densely scaled, rostrum very long, in side view almost straight to the antennal insertions and then curved to the apex, always distinctly longer in the female. Antennae long and slender; the scape broadened just before the apex, all funicular segments elongate and the club elongate and slender. Pronotum slightly transverse, almost parallel-sided in the basal half and strongly narrowed to a subapical constriction, basal and apical margins weakly curved, surface more convex towards the base, densely scaled throughout along the centre with weakly raised and intermeshed scales that form a low ridge, this is very variable and usually only obvious towards the base. Scutellum elongate and covered with pale, sometimes almost white, scales; this elongate shape will distinguish venosus from our other members of the genus, all of which have the scutellum slightly transverse or, at most, quadrate. Elytra broadest behind widely-rounded shoulders and narrowed to a continuously-curved apical margin, the scales are dense and the pattern is usually distinct but the punctured striae are visible throughout, towards the apex the scales form a low but distinct crest. All femora with a strong ventral tooth. Females can be distinguished by the longer rostrum and having the antennae inserted at or behind the middle, in males the antennae are inserted beyond the middle of the rostrum.