Crepidodera plutus (Latreille, 1804)
This widespread species occurs throughout the Palaearctic region from Portugal to Northern China, Korea and Japan, extending north to the UK and southern Sweden, it is generally common across central and southern Europe but much less so in the north; it is sporadic and scarce in Poland and Denmark and absent from Fennoscandia except for the south of Sweden where it has been introduced. Here it is locally common across southern and central England north to South Yorkshire but mostly absent from the West Country and sporadic and very local in Wales. Adults are present year-round, they become active in early April and peak n abundance from May to July and again in September, they overwinter under bark or among leaf-litter near to the host trees and regularly occur in winter extraction samples. Hosts include various narrow-leaved willows, Salix spp, especially S. fragilis L. (Crack-willow) and S. caprea L. (Goat willow) but any willow is likely to host the beetle, they also occur on various poplars, Populus L. though much less commonly so, and have been recorded from Prunus spinosa L. (Blackthorn). Typical habitats are wherever mature host trees occur; wetlands of all kinds, heathland, moorland, woodland and roadsides and often on larger trees in parks and domestic gardens. Adults feed on beneath foliage, stripping the epidermis but leaving the leaf otherwise intact, they also feed on pollen and in the spring may be observed on a range of flowers, reproduction begins in the spring and mating pairs may be observed into early summer. Oviposition occurs over a long period, from May until July, eggs are laid singly or in small groups on the underside of leaves and larvae emerge after one or two weeks, they drop to the ground and burrow into the soil where they feed externally on the host roots, development is rapid and pupation occurs in an earthen cell among the roots from early summer, the new-generation adults appearing during August and September when they may swarm around host foliage. The species is univoltine and adults are capable of flight, they might occur in any situation on host trees and are readily sampled by sweeping or beating foliage during the warmer months, during the warmest summer days they might also be found among grass or on other trees remote from the host.
Members of this genus are readily recognized among our UK fauna by their small size, elongate form and bright metallic colouration and the present species is readily distinguished by its abruptly bicoloured antennae, the basal four segments pale orange or yellow and the rest black or dark brown. 2-3mm. Form elongate and rather parallel-sided, the dorsal surface shiny metallic coppery, green, blue or brassy, often with the forebody or pronotum contrasting. Head transverse with large convex eyes that contact the pronotum, vertex very finely punctured and indistinctly microsculptured (X20), antennae inserted anteriorly beside the eyes, the insertions separated by a little less than the length of the basal segment. Pronotum transverse (3:1), broadest about the middle and narrowed to sharp anterior and posterior angles, lateral and basal margins finely bordered, the lateral margin toothed about the apex. Surface strongly but sparsely punctured, a little more densely so laterally, towards the base with a transverse furrow joining elongate basal fovea. Scutellum smooth and shiny, contrasting with the surrounding cuticle. Elytra with rounded shoulders and a continuously rounded apical margin, each with ten strongly punctured striae, the outermost very close to the lateral margin, and an abbreviated scutellary striole, interstices very finely punctured and indistinctly shagreened so that they appear slightly dull, and the sutural interstice depressed subapically. Legs substantially yellow with the posterior femora and the terminal segment of all tarsi black. Claws strongly appendiculate.