Apion rubiginosum Grill, 1893
This species occurs sporadically throughout Europe from Portugal to Greece in the south and north to the UK and southern provinces of Fennoscandia, it occurs locally across North Africa and Asia Minor and extends through Russia and Kazakhstan into Central Asia. In Europe, where it occurs from lowlands to middle mountain altitudes, it is locally common in southern and central regions but becomes scarce and very local in the north. In the UK it is locally common in the Brecklands of West Norfolk and West Suffolk but otherwise very local and rare; mostly across south east England but also in the West Country, Wales and Anglesey where it tends to be mostly coastal, and further north to the Lake District. Typical habitats are open sandy heaths, moors, grassland and dunes where the host plant is abundant. Adults are present year-round; they overwinter among litter or tussocks etc. and are active from March or April until October or November, depending on the season, and peak in abundance during late summer. The species is monophagous on Sheep’s Sorrel (Rumex acetosella L.). Mating occurs early in the spring following a period of feeding on emergent host foliage and females oviposit among host roots or stems from mid-May. Larvae develop inside the roots, eventually forming irregular galls about a centimetre across, when fully grown the larvae are 5-10 mm long and there may be two or more in several chambers within a single gall. Pupation occurs within the gall and adults emerge to feed from August, they generally remain active on host foliage into November when they leave to find overwintering sites, usually near to the host plants. Adults can be sampled by sweeping and they usually occur in numbers but they will need to be looked for very carefully as several very similar and common species also use this host.
2.2-3.2 mm. Elongate and narrow but with relatively broad elytra which are curved laterally and widest at or slightly behind the middle, entirely orange to dark red, sometimes with the tarsi a little darker, and with fine pale pubescence throughout. Superficially similar to our other members of the genus but distinguished by the following combination of characters. Rostrum almost straight in lateral view (in males often weakly curved above) and only weakly angled with the head ventrally at the base. Head slightly elongate with temples punctured and pubescent behind the eyes but with a wide, mostly unpunctured and transversely striate area between this and the base. Elytra not more than 2.5X longer than the pronotum which is quadrate or very slightly elongate. These characters combined are usually sufficient; only A. haematodes has similar temples and pronotum but has a shorter (shorter than the pronotum in both sexes) and distinctly curved rostrum and more strongly rounded elytra. In rubiginosum the rostrum is sexually dimorphic; in males broader, at most as long as the pronotum, in females narrower and as long as or longer than the pronotum.