Sitona striatellus Gyllenhal, 1834
This widespread species is generally common from lowland to mid-mountain altitudes throughout Europe from Spain east to Asia Minor, Ukraine and western parts of Russia; it is present on most of the Mediterranean islands but absent from North Africa, in the north it extends to the UK, Denmark and the southern Baltic countries but does not reach Fennoscandia. It is common across Wales and England as far as Yorkshire, including the Isle of Wight, Anglesey and Man, and much more local and scarce in Northern Ireland and further north to the Scottish Highlands which represent the northernmost limit of its European distribution. Adults occur throughout the year and are active over a long season from early spring until autumn, peaking in abundance during spring and late summer, they occur in a range of habitats where the host plants are common, typically dry grassland and meadows, hillsides, woodland margins, wasteland and sandy areas, on the continent they are common in open woodland and often abundant in pine forests. Host plants include various species of Ulex L. but especially common gorse (Ulex europaeus L.), dyer’s greenweed (Genista tinctoria L.), hairy greenweed (G. pilose L.) and various species of broom; in the UK typically on common broom (Cytissus scoparius (L.) but on the continent also on other wild species and cultivars, adults may also feed on the foliage of other Fabaceae such as peas (Pisum sativum L.) but herbaceous species do not host the larvae. Adults appear early in the year and feed on freshly emerging foliage, they mate in the spring and this may follow a short dispersal flight. Females oviposit into the soil below host plants and larvae develop through the spring and summer feeding ectophagously on nitrifying root nodules, they are fully grown by July or August and pupate in the soil to produce new-generation adults from August which will go on to overwinter in the soil or among tussocks or litter. They are easily sampled by beating or sweeping host foliage but they occasionally occur away from their normal hosts, especially on hot summer days.
Our UK members of Sitona can be very difficult to identify but sampling the present species from its host plants is a very good indication of its identity, two broadly-similar species, Andrion regensteinense and Polydrusus confluens, occur on the same hosts but these should be obvious by careful examination. 2.8-4.8 mm. Elongate and rather parallel-sided, forebody with pale scales that form lines on the pronotum, elytra with longitudinal lines formed of pink, green and creamy scales that appear metallic in places, and short curved setae that become semi-erect towards the apex, legs pale brown with dark femora, antennae dark brown with the apex of the scape and the club lighter. Head with pale oval or elongate scales which diverge obliquely from a narrow longitudinal impression, those towards the end of the rostrum finer and paler, eyes convex and symmetrical, the vertex between almost flat and with strong slightly elongate punctures that are confluent in places, antennal scape gradually and moderately thickened from the apical third. Pronotum broadest at or slightly behind the middle (this varies and specimens may appear distinctly different in this respect) and smoothly curved to an obtuse basal angle and a distinct subapical constriction, surface smoothly convex with strong, elongate and often confluent punctures throughout, the cuticle between smooth and shiny, the pale scales form distinct median and lateral longitudinal lines and the fine setae are curved and directed forward. Prosternum with a distinct transverse impression behind the apical margin which joins, or at least touches, the anterior margins of the coxae. Elytra strongly punctured and rugose, the black cuticle obvious among the scales even in fresh specimens, the oval, teardrop-shaped scales include a mixture of colours but form contrasting lines, those on odd-numbered interstices usually distinctly paler although the lateral elytral margins may be extensively pale, curved setae more obvious towards the apex where they usually form distinct longitudinal rows. Males mat be distinguished by the presence of a small tooth at the internal apical angle of all tibiae, in females it is simply angled.
Important identification features include the degree of thickening of the antennal scape, the size and convexity of the eyes, the proximity of the front coxae to a distinct subapical impression and the presence of semi-erect curved protective setae on the elytra, most obvious towards the apex. The overall colour varies from pale brown or bronzy to dark grey, always with contrasting paler longitudinal bands of scales.