Exapion fuscirostre (Fabricius, 1775)
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POLYPHAGA Emery, 1886
CURCULIONOIDEA Latreille, 1802
EXAPIINI Alonso-Zarazaga, 1990
Exapion Bedel, 1887
This locally common weevil occurs throughout Wales and England north to Nottingham, it is mostly coastal in the West Country and scarce and sporadic further north as far as Cumbria. In our local South Hertfordshire area it was very common until only a decade ago but we now rarely see it in numbers despite an abundance of its host plant, common broom (Cytisus scoparius L.). Beyond the UK it is occurs throughout Europe north to the south of Fennoscandia, across North Africa and the Near East and into Ukraine and Western Russia, it has also become established in North America since being introduced from Europe in the early 1960s to help control broom. Adults are present year-round and may be particularly common in early summer as overwintered specimens are still present as the first new-generation appears; overwintered adults become active early in the year and feed on tender foliage and shoots for a while before mating, which may continue into June. Females lay a few eggs into developing seed pods and larvae emerge after one or two weeks, they feed on the outside of the seeds and will usually consume most of a single seed as they grow, they develop rapidly and pass through three instars within twenty to forty days before pupating inside the pod. The pupal stage lasts about three weeks and the resulting adults remain within the pod until it dries and opens naturally. Adults may occur wherever the host plants are common but seem to prefer open and dry sites, particularly among grassland on south-facing slopes, locally they occur in small numbers and usually among larger populations of other members of the genus but large populations sometimes occur and adults may appear in new sites soon after the host is introduced as they are known to disperse up to two kilometres during the summer.
Adults are small, 2.4-3.0mm, and distinctively coloured; the body is dark grey or greyish-brown and the appendages are substantially red, the forebody is clothed with long pale setae-like scales and the elytra have two longitudinal strips of pale scales, one at the base of the fifth interstice which reaches to about a third of the elytral length, and another mostly along the third or fourth interstices on the disc but often connected obliquely to those on the fifth. The present species is distinguished among our fauna by the strong tooth at the base of the rostrum combined with pale legs and coarse pale scales forming a pattern on the elytra. The form is long, slender and very convex, in cross section the elytra are distinctly higher than wide, the head is transverse with large convex eyes, the pronotum slightly transverse and broadest behind the middle and the elytra are highly arched in side view. Antennae entirely red, legs red with the femoral base, tibial apices and tarsi darkened. Claws separate and strongly curved, each with a small and sharp tooth at the base. Males may be distinguished by the presence of a small tooth under the apex of the basal meso- and metatarsomere but they are usually narrower and more parallel-sided and have a shorter rostrum than females and so soon become obvious even in the field.