Drupenatus nasturtii (Germar, 1824)
The only species of the genus Drupenatus Reitter, 1913, this is a locally common weevil through most of Western Europe and Northwest Africa; in the U.K. it occurs through England and Wales, including Anglesey, north to the Humber, and further north there are a few records from Cumbria. This is a wetland species associated with various cresses, in the U.K. especially on Nasturtium officinale, watercress, and N. Microphyllum, onerow yellowcress. Adults occur from early spring, feeding on the leaves, and may often be observed in the flowers. The larvae develop within the host stems and were formerly a minor pest of commercially grown cress, especially on the continent. Typical habitats are wetland wherever the host thrives; generally slow-moving rivers, ditches and streams, especially in chalk and limestone areas. Adults persist through the spring and early summer and may be swept from the host and surrounding vegetation but they rarely occur in numbers. New generation adults appear in the summer and autumn and feed before overwintering in tussocks, moss and litter etc. near the host. With a little patience they may be observed on the host foliage but when disturbed they will often drop to the water upon which they are able to walk to nearby stems or substrate.
The characteristic broad-oval and flattened form and grey, green or brown metallic dorsal surface will soon become familiar. 2.9-3.6mm. Head with broadly oval scales laterally and dense long pubescence on the vertex, eyes convex and coarsely faceted, rostrum long, parallel and largely devoid of scales. Antennae pale, the scape long and thickened from the middle, funiculus 7-segmented and the club compact and narrow. Pronotum transverse, strongly narrowed from the base and constricted before the apex; viewed from in front the margin is simple i.e. without the double border seen in some ceutorhynchine groups, surface strongly and closely punctured, with short broad scales which extend around the lateral margin , and dense setae medially, generally with a longitudinal furrow along the middle. The hind margin is sinuate; produced towards the small but usually obvious scutellum. Pro-coxae close together but not touching, the rostral channel ending just anterior to these. Meso-coxae separated by less than the width of a coxa. Elytra broadly oval, flattened and separately rounded, with distinct striae which usually have a row of broad pale scales, interstices densely and finely punctured, much broader than the striae, with broadly oval scales, and long pale setae generally arranged in a broad V-shape from the humeri to the middle, all interstices are smooth, lacking tubercles. In older specimens the scales may be rubbed, especially behind the scutellum. Legs long and robust; colour variable but generally pale with the femora darker, all femora with a small ventral tooth; tibiae sinuate, the meta-tibiae as broadly dilated at the apex as the meso-tibiae, not expanded into a tooth. Male meso- and meta-tibiae have a small apical spur.
Drupenatus nasturtii 1
Drupenatus nasturtii 2