Tachyerges salicis (Linnaeus, 1758)
Native to the entire Palaearctic region, including Japan, this species has also become established and widespread across the United States and Canada and so has a Holarctic distribution, it is locally common throughout Europe from the Mediterranean to the far north of Fennoscandia and the UK. Here it occurs throughout England and Wales and there are a few widely scattered records from Scotland and while it may be locally common it is very rarely seen in numbers. Typical habitats are wetland margins, damp woodland and carr where the hosts, which include various willows, are common but we have also recorded them from isolated trees in parks and gardens and they seem to occur mostly on younger trees and saplings. On the continent they are also recorded from Populus tremula L. and other species of the genus. Adults overwinter and become active in early spring when they begin feeding on freshly emerging host foliage, reproduction occurs in the spring and oviposition continues through spring and early summer. A single egg is placed on or near the main vein on the underside of a leaf, usually towards the leaf apex, and is covered with a protective secretion but unlike those of many hopping weevils this does not cause the vein to expand and crack, the larvae emerges within a few days and begins to mine the leaf, always towards the apex and eventually producing an irregular blotch mine which will occupy up to a third of the leaf and cut across veins. The mines are initially dark brown but soon turn a translucent creamy colour as they are hollowed out, leaving narrow trails of dark frass and a darker area where the pale orange larvae are usually clearly visible. Fully-grown larvae have been recorded from late spring to late summer, perhaps suggesting a second generation, they construct a cocoon from secretions and pupate within the mine and adults eclose soon after. Adults may be swept from host foliage through the spring and summer and are usually found as single specimens.
Tachyerges salicis 1
Tachyerges salicis 2
2.2-2.8mm. An unmistakable species due to its very distinctive colour and elytral pattern. Substantially black with scattered pale scales to the pronotum and two irregular transverse bands of pale scales to the elytra, one behind the middle which usually does not reach the lateral margins and one towards the base, the internal part consisting of a long inverted V of contrasting yellow scales which extends anteriorly to the scutellum. Head coarsely punctured, with large eyes that meet along their inner margins and a weakly curved and moderately broad rostrum which is longer in the female. Antennae pale with the club darker, distinctly geniculate, the scape as long as the following three segments, funiculus 7-segmented with the basal segment much broader than the following, club slender and pointed. Pronotum transverse, broadest behind the middle and strongly narrowed to straight apical margin, basal margin smoothly curved, surface very strongly punctured, these are mostly distinct but become confluent and confused on the disc. Scutellum with dense white scales which contrast with the adjacent creamy-yellow elytral scales. Elytra broadly-oval with sloping shoulders and smoothly curved laterally to a continuously rounded apical margin, striae strongly punctured and complete to the apex and interstices finely punctured throughout, vestiture consists of a distinctive pattern of coloured elongate scales and very fine recumbent scale-like pubescence. Legs long and robust, black but appearing grey due to moderately dense pale scales, hind femora enlarged. Claws yellow, contrasting against the dark tarsi, each with a sharp tooth at the base.