Bruchidius villosus (Fabricius, 1792)
This native Western Palaearctic species occurs throughout Europe from Portugal to Turkey and north to Southern Scandinavia and Russia, it was accidentally introduced to the United States around 1918 but was found to be an effective control measure against the invasive Scotch Broom, Cytisus scoparia (L.), and so there have been further introductions and it is now established and widespread, it has also been introduced to New Zealand for the same reason but has been found to attack other plants and so its use has been limited. It is locally common throughout its native range including the UK where it occurs throughout England and Wales though less frequently so in the north and is so far absent from Scotland. Typical habitats include moorland, wasteland, wooded borders and parkland but it may be encountered wherever the hosts occur, in the UK it is usually associated with Scotch Broom but more generally also on other species of Cytisus, Genista and Laburnum. Adults overwinter, occur very early in the year, from February or March, and may be found until October or November; they are fully-winged and disperse by flight in the spring and so may suddenly appear in new habitats. Adults feed on pollen, typically on the host but they have been recorded from a range of flowers including Yarrow, Achillea millefolium L., and Hogweed, Heracleum sphondylium L., after emerging from their overwintering quarters in tussocks etc. they assemble on Gorse and feed in the flowers, mating occurs at this time but when the Broom begins to flower they move to this new host to continue feeding and begin oviposition. Eggs are laid during May and June on newly-developing seed pods, up to 10 on each pod, and larvae emerge after about 3 weeks, they chew through the base of the egg and into the seed case where each will enter a developing seed and complete its development; they pass through 4 instars and are fully developed within 2 or 3 weeks. The larva leaves the seed and pupates within the pod, this stage is brief and adults eclose and remain within the pod, they cannot chew through to escape but wait until the pod dries and splits open. New generation adults occur from June and as those of the previous generation still persist this is the time of peak abundance, the latest adults will remain on the host into the autumn when they will enter grass tussocks etc. to overwinter.
Bruchidius villosus 1
Bruchidius villosus 2
Bruchidius villosus 3
A small species, 2.4-3.2mm, entirely dark brown or black, including the abdomen, with the basal 3 or 4 antennal segments red, at least underneath, dorsal surface with quite dense short and pale pubescence. Head produced anteriorly, with short temples narrowed strongly narrowed to the base and convex, deeply emarginate eyes; the surface densely and quite strongly punctured. Palps dark, terminal segment long and narrow. Antennae relatively long, extending to at least the pronotal base, segments 1-4 elongate, 5 and 6 quadrate or nearly so and 7-10 transverse, terminal segment elongate and rounded. Pronotum widely transverse, about twice as wide as long; broadest at sharply acute posterior angles and narrowed to a rounded anterior margin, lateral margin smooth, without a denticle, and basal margin broadly produced across the middle. Elytra broadly oval and separately rounded apically leaving the pygidium and the previous tergite at least partly exposed, each with 9 striae complete to before the apex and uniformly distributed pale recumbent pubescence. Pygidium quadrate, triangular and evenly and rather densely pubescent. All femora smooth underneath, without teeth. Tarsi 5-segmented; basal segment elongate, third deeply lobed and often concealing the tiny fourth segment. All claws with a large and sharp basal tooth.