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Anthribus nebulosus Forster, 1770







POLYPHAGA Emery, 1886

CURCULIONOIDEA Latreille, 1802

ANTHRIBIDAE Billberg, 1820

ANTHRIBINAE Billberg, 1820

ANTHRIBINI Billberg, 1820

Anthribus Geoffroy, 1762

Widespread and locally common throughout Europe except for the far north and extending east through Asia Minor and Russia into Siberia, it has also been intentionally introduced as a biocontrol agent into North America on several occasions since the 1970s and is now established and spreading. This species occurs locally across southeast and central England and eastern parts of Wales, it is absent from the West Country and sporadic and generally rare further north to the Scottish border. Typical habitats are coniferous, and to a lesser extent deciduous, woodland and wooded parkland, and adults may be found year-round; they are mainly diurnal and spend most of their time on the surface of small branches, twigs and foliage but in warm weather they also occur on flowers, especially hawthorn blossom and umbels on wooded borders, they are active over a long season from April or May and spend the winter under bark or in crevices, often in numbers. Unusual among the family, members of this genus are predators of various scale insects (Hemiptera, Coccoidea) which infest a range of trees and shrubs but conifers seem to be preferred and, at least in northern Europe, they are most common on spruce (Picea Mill.). Following their emergence in the spring both sexes feed for a while on soft scales before mating, this occurs close to scale colonies and lasts for about twenty minutes, after which the female will begin searching for suitable oviposition sites, here she will examine scale insect brood pouches with her antennae to ensure they have not already been parasitized and, after choosing a suitable host, will bite a small hole into the underside and insert a single egg. Oviposition continues into the summer and each female will produce between twenty and thirty eggs. Larvae emerge after a few days and feed on host eggs within the pouch, they develop rapidly and will generally consume all the eggs present, the duration of each of the three larvae stages depends on the host species and on the number of eggs present but the first two stages take about a week each while the last stage may take a few days longer. Pupation occurs within the host egg pouch and this stage lasts on average for eight days. The entire cycle generally takes between forty and fifty days and freshly eclosed adults occur during June, these are soft and pale and usually remain in the pupal case to harden and darken, they then consume the remains of the brood pouch and may become active for a while before entering into their overwintering quarters or they may remain in place and enter into diapause until the following spring. Adults do not mature until they have overwintered and spent some time feeding in the spring and so there is a single generation each year. Sampling usually involves sweeping or beating infested branches or foliage during spring or early summer but adults may sometimes appear among samples of bark or debris from living trees.

Anthribus nebulosus

Anthribus nebulosus

2.5-4.6mm. A very distinctive weevil which should be obvious from its general appearance, it may be distinguished from other UK anthribids by the smooth pronotum, which lacks a sub-basal keel, the small size and the antennal insertions which are placed laterally on the rostrum and not visible from above. Body dark brown or grey with areas of paler scales to the head and pronotum and patches of raised pale pubescence on the odd-numbered interstices. Head transverse with protruding and convex eyes and a short and broad rostrum. Antennae 11-segmented with an elongate and compact club. Pronotum broadest across acute posterior angles and narrowed to a rounded anterior margin, surface evenly convex and lateral margins bordered only in the basal half. Elytra elongate and broad with rounded shoulders and near-parallel lateral margins. Striae strongly punctured and complete, interstices much broader than striae and almost flat across the disc.

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