Parathelcus pollinarius (Forster, 1771)
This generally common species occurs throughout Europe and North Africa north to the UK and Scandinavia and east through Asia Minor to Kazakhstan and western Russia; here it is locally common through England and Wales though absent from the West Country and very local and scattered in the north and Scotland. Adults occur from March to October; they are common in the spring and early summer, generally scarce during the warmer months and then appear again from September but in lower numbers than in the spring. They are monophagous on nettles, Urtica dioica, and generally occur in damp and shaded habitats e.g. woodland margins, gardens and extensive nettle beds in parkland and along river margins etc. Adults may be sampled by beating and sweeping the host and in early spring they may appear among other low vegetation as they disperse, they usually occur among larger populations of Nedyus but usually only as pairs or single specimens. Mating occurs in the spring and oviposition continues from April to June; eggs are laid in a small cavity bored low down in the stem or into a large petiole and larvae mine down through the stem to ground level where they form a characteristic swelling as they feed, they then bore into the soil to pupate. New generation adults from early spring eggs appear from midsummer, increasing in numbers into the autumn, these will feed on host foliage and flowers before overwintering in the soil, but larvae developing later in the summer will overwinter low down in the stems and pupate in the soil from February the following year.
Adults soon become familiar from the flattened appearance, angular pronotum and dull grey colour with a patch of pale scales at the apex of each elytron. On average they are distinctly larger than Nedyus.
2.8-4.0mm. Broad-oval and discontinuous in outline, entirely black but for the red tarsi and antennae, the dorsal surface appearing predominantly grey from mixture of brown, grey or bluish-grey and while scales. Head strongly and densely punctured, with large convex eyes and a long and punctured rostrum. Antennae inserted near the apical third of the rostrum, nearer the apex in the male, scape gradually broadened towards the apex, funiculus 7-segmented and the club long and pointed. Pronotum transverse (3:2) with a strongly raised and sharply pointed dorso-lateral tubercle and raised anterior margin, the surface strongly and densely punctured and with a variously developed longitudinal impression which is usually obvious towards the anterior and posterior margins. Scutellum small and sometimes barely visible. Elytra quadrate with prominent shoulders, weakly impressed striae and flat interstices which are tuberculate above the apical declivity; the ninth with a series of tubercles from near the base to the apex, each bearing a short dark seta. Each elytron with a patch of white scales below the declivity although these are continuous in some specimens. All femora with a strong ventral tooth, in the male the meso- and meta-tibiae have a spur at the inner apical angle.