Oxystoma pomonae (Fabricius, 1798)
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POLYPHAGA Emery, 1886
CURCULIONOIDEA Latreille, 1802
OXYSTOMATINI Alonso-Zarazaga, 1990
Oxystoma Duméril, 1806
Among the most common and widespread members of the genus, this species occurs throughout Europe north to the UK and southern Fennoscandia, across North Africa and the Near East and extends east into central Siberia. Here it is locally common and sometimes abundant across northern Wales and England north to Nottingham, and very scarce and local in the West Country, South Wales and further north to the Scottish border. Host plants include various Papilionaceae; in the UK typically bush vetch (Vicia sepium L.), common vetch (V. sativa L.), tufted vetch (V. cracca L.) and meadow vetchling (Lathyrus pratensis), but on the continent other hosts such as tuberous vetchling (L. tuberosus L.)and great wood-vetch (Vicia dumetorum L.) have been recorded. Adults occur from April until August or September and habitats include anywhere the host plants are abundant, typically waste ground, agricultural ground, road verges and disturbed places generally; they may be swept from host foliage but may also occur on a range of trees and shrubs and on the continent have been recorded feeding on anthers and soft needles of pine saplings in nurseries. Reproduction begins in the spring and continues until the end of June when mating pairs may be observed on host foliage and developing seed pods, Females lay small batches of eggs into unripe seed pods where the developing larvae feed on unripe seeds; they pass develop rapidly, passing through 3 instars and pupating within the pod from early July. Each larva needs to consume 2 seeds to complete its development and a single pod may contain 4 or 5 larvae, by late July the pupae are fully developed and at this time opened pods may reveal a row of pupae or freshly eclosed, soft and yellow adults. These adults remain within the pods for a few days as they gradually harden and develop their pigment, they then emerge and may become active for a while or may enter the ground or hide among moss or litter where they will pass the winter before emerging and feeding on developing foliage in the spring.
Species of Oxystoma Deméril, 1805 are easily recognized by the large convex eyes and the shape of the rostrum which from above is strongly narrowed towards the apex and from the side angled down from the front of the scrobes to the apex, the present species is distinguished among our fauna by its metallic blue or bluish-green metallic lustre. 2.5-3.6mm. Entire dorsal surface with sparse pale recumbent pubescence. Head and rostrum as far as the preapical narrowing strongly and often confluently punctured, between the eyes indistinctly longitudinally striate, eyes large and coarsely faceted and temples long and parallel-sided. Antennae dark with the scape and one or two funicular segments pale. Pronotum quadrate and campanulate, with indistinct anterior angles and protruding posterior angles, surface strongly and discretely punctured and with a sharply defined longitudinal impression in the basal half. Elytra broadest about the middle, with sloping shoulders and sinuate before the apex, all striae well-impressed and strongly punctured; the sutural striae not reaching the basal margin but complete to the apex, interstices at least twice as broad as the striae, and each with two or three rather random rows of fine punctures. Legs entirely dark. Male rostrum shorter than the pronotum and broader and less strongly narrowed in side view; female rostrum as long as the pronotum and narrower and more strongly narrowed in side view.