Protopirapion atratulum (Germar, 1817)
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POLYPHAGA Emery, 1886
CURCULIONOIDEA Latreille, 1802
OXYSTOMATINI Alonso-Zarazaga, 1990
Protopirapion Alonso-Zarazaga, 1990
One of only 2 European members of the genus this species occurs throughout Europe and northwest Africa north to Denmark and the UK where it is widespread though local across Wales and England north to the midlands and scattered and rare further north. Host plants include various species of Ulex, Genista and Cytisus; adults overwinter and appear from April or May and begin feeding on freshly developing shoots and foliage, mating occurs soon after and females begin searching for developing flower buds in which to oviposit. After finding a suitable small bud she will bore into it from below, insert a single egg and then seal it with a drop of clear fluid from her abdomen before searching for other flower buds. Larvae hatch after a few days and feed on the stamens, anthers and stigma, causing the stem and base of the bud to turn brown, during feeding the stem is gradually eaten away and when fully-grown, after 2 or 3 weeks, the larva seals the bud and severs the stem so that it falls to the ground. For a short while after falling the larva is able to make the bud ‘jump’ for short distances, this may deter parasites or move the bud away from unfavourable conditions, and it may continue for several hours after which it stops unless the bud is exposed to changes in temperature or is moved. Pupation occurs inside the bud after a week or so and adults eclose within 7-10 days. The freshly emerged adult is slender, soft and pale, it bores a small hole through the bud and can squeeze through before it hardens and acquires its characteristic very broad-oval form. This new generation, appearing from June and into the summer, will remain on the host feeding on fresh foliage into the autumn when they will descend the stems to overwinter among soil and tussocks etc. around the base of the plant. Adults are easily sampled by beating or sweeping foliage and stems but while they are generally common in suitable habitats they usually occur in small numbers; established populations may last for many years but the species is wingless and habitats recently colonized by the hosts rarely produce the weevils.
A small species, 2.2-3.2mm, characterized by the shape of the elytra, with narrow sloping shoulders and broadly dilated and rounded apically; this form is also seen in Pirapion immune (Kirby, 1808), which occurs on the same hosts, but here the frons is strongly striate and the pronotal furrow is short, not extending to the middle. Head with large and coarsely-faceted eyes, frons and vertex variously punctured or rugose but not, or only very finely and vaguely, striate, rostrum long and cylindrical or weakly broadened by the antennal insertions; in the male as long as the head and pronotum, in the female longer. Antennae long and robust, scape long, weakly curved and abruptly thickened towards the apex, club slender and pointed. Pronotum broadest before the base and narrowed to indistinct anterior margins, surface strongly and densely punctured, with a deep basal fovea extending beyond the middle. Elytral base about as broad as the base of the pronotum; without distinct shoulders and strongly dilated apically, striae strongly impressed and punctured; complete to the apex but the sutural stria abbreviated about the scutellar apex, interstices broad and flat, the surface finely rugose and each with several confused rows of pale pubescence. Legs long and robust, entirely dark and finely pubescent. Basal tarsomeres without a ventral tooth, all claws with an obtuse internal tooth.