Crepidodera plutus (Latreille, 1804)
A local and sometimes common species occuring throughout southern England and the midlands north to Liverpool and York and west to Dorset and Somerset, and there are a few records from eastern Wales. They occur throughout our Watford area; generally, though not necessarily, in wetland habitats and usually in small numbers, often among much larger populations of C.aurata. Host plants are various species of willow (Salix) but more especially crack-willow (S.fragilis) and, less often, poplars and blackthorn (Prunus spinosa). Konstantinov (1996) lists S.daphnoides and Populus spp. Adults may also be found on flowers eg they have been recorded from dandelion. There is a single generation each year with adults hibernating under bark etc. and we have recorded them during January from grass tussocks growing beneath Salix in Cassiobury park. They become active early in the spring when the host comes into leaf and feed on the undersurface of the leaves. Eggs are laid singly or in small groups on the underside of host leaves from May to June or July and they hatch within two weeks, larvae feed on the roots and pupation takes place in the soil. New generation adults occur late in the summer and are active until the leaves turn yellow, they have been observed swarming during September and October (Cox). Adults are easiest recorded by beating or sweeping willows although, locally, most specimens will be C.aurata and so will need to be examined; plutus is unicolorous bright metallic and very variable in colour but unique among our species in having the basal antennal segments pale yellow or orange and contrasting against the distal black segments, this is easily observed in the field at X10. On hot summer days they disperse and may be found in many situations away from the host plant eg during August 2008 we swept them from long grass and from oak foliage in Cassiobury park and from hawthorn on the borders of West Herts golf course.

2-3mm. (Joy). Elongate and subparallel, upper surface very shiny and variable in colour, grren or blue or a combination of those and with a strong metallic coppery or bronze or golden reflection. Antennae inserted near front margin of eyes; distance between insertions less than half the length of the basal segment, colour will distinguish C.plutus from other British species; black with three or four basal segments and sometimes the base of the fifth segment clear yellow and strongly contrasting. Eyes large and very convex, occupying almost the entire side of the head and touching the pronotum in normal setting Vertex very finely punctate and indistinctly microsculptured (X20). Pronotum transverse (3:1) with lateral and basal margins finely bordered. Front angles denticulate, side margins smoothly rounded then sinuate before almost perpendicular hind angles. Surface strongly but sparsely punctured, more densely so laterally, with a short longitudinal furrow either side at base joined by a deep transverse furrow. Scutellum smooth and shiny, contrasting with the surrounding elytra. Each elytron with ten strongly punctured striae, outermost very close to lateral border, as well as an incomplete sutural stria from base to about one third. Interstices very finely punctured and indistinctly shagreened so that they appear slightly dull. Apices evenly rounded to suture which is depressed just before apex. Legs testaceous with hind femora and last segment of all tarsi black. Claws strongly appendiculate.

Description from 4 Watford specimens at X20

Reference
Konstantinov, A.S. 1996 Review of palearctic species of Crepidodera. Spixiana 19/1:21-37.

see ID Aids for a key to the genus.

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