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Polydrusus confluens Stephens, 1831







POLYPHAGA Emery, 1886

CURCULIONOIDEA Latreille, 1802

CURCULIONIDAE Latreille, 1802

ENTIMINAE Schönherr, 1823

POLYDRUSINI Schönherr, 1823

Polydrusus Germar, 1817

This is a very widespread lowland species of south and central Europe extending north to Denmark, where it is very local and rare, and the UK where it is widespread though local and mostly coastal around southern England and Wales. The typical habitat is open dry grassland, dunes, heathland and scrub where the hosts, various gorses and broom, are abundant. During June 2018 we found large populations on gorse behind busy public beaches in South Hampshire. Adults occur from May to August and feed on young foliage and tender shoots, oviposition begins after a period of feeding and continues through the season. Eggs are laid singly or in small batches in the ground around the host and larvae develop underground; feeding externally upon the roots of the host etc. they are fully developed by late summer or autumn but remain in the soil overwinter and pupate in a subterranean cell in the spring. Adults are flightless and easily sampled by beating or sweeping foliage and usually occur in numbers.

4.3-5.5mm. Superficially similar to some Sitona, especially where the pale stripes of scales contrast against the darker ground colour, but with the claws connate. Head smooth; without a median longitudinal impression, with prominent and slightly asymmetrical eyes, long temples which diverge basally and a relatively long and near parallel-sided rostrum; the scrobes curve down below the eyes and are usually without scales, antennae long and slender; scape weakly curved and gradually broadened towards the apex, segments 2-8 elongate and rather abruptly thickened at the apex; 6-8 about twice as long as broad, club short and slender. Pronotum weakly transverse in the male, more strongly so in the female; evenly rounded laterally and broadest at, or a little in front of, the middle. Typically dark with a longitudinal band of pale scales towards each lateral margin but this can vary in strength. Elytra with sloping shoulders and only a little broader than the pronotum, parallel-sided in the male but curved and broadest towards the apex in the female; typical colour consists of an unmetallic brown or grey and often mottled background with the third interstice paler from the basal fifth or so, the fifth interstice pale at the base and the lateral margins often extensively pale. Striae consist of rows of quite strong punctures which are usually obvious among the scales. Legs long and robust, especially the forelegs; all femora with a strong ventral tooth, tibiae expanded and incurved at the apex, third tarsomere strongly bilobed, claws fused at the base. The colour is also reminiscent of some Sitona; the femora are usually dark, sometimes narrowly red at the apex, the tibiae extensively pale and the tarsi dark.

Polydrusus confluens

Polydrusus confluens

© Lech Borowiec

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