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.