Psylliodes Latreille, 1829
This is a large and cosmopolitan genus of more than 200 species with the greatest diversity in the Palaearctic and North African regions, and almost 100 species occur in Europe and Asia Minor. By contrast less than 20 species occur in the Nearctic region and 6 of these are adventive. The genus is represented in Europe by 3 subgenera but two of these are monotypic; Eupus Wollaston, 1854 includes a Madeiran endemic, and Semicnema Weise, 1888 includes a widespread species of South-eastern Europe, Ukraine and southern Russia. Many species are widespread across the Palaearctic region but the genus also includes many localized and Island endemic species. The U.K. fauna includes 15 species of which one, P. luridipennis Kutschera, 1864 is endemic to Lundy. They are small, <5mm with the majority around 3mm, and distinctive with compact elongate-oval bodies and greatly enlarged hind femora. The majority are dark brown or black and distinctly metallic but many vary from pale yellow to brown, often with the fore-parts and elytra contrasting and often with the elytral base and/or suture darkened. The colour varies in many species and this has generated a huge number of named aberrations, and many occur as distinct subspecies. They are distinguished from other European chrysomelids in having the antennae 10-segmented, the hind femora enlarged, sometimes greatly so, and the hind tarsi inserted before the apex of the tibiae; in subgenera Eupus and Semicnema it is inserted about half way along. The antennae are proportionally long and the head is usually visible from above, P. cucullata (Illiger, 1807) is an exception in having the head concealed from above by the pronotum. The latero-orbital and clypeal impressed lines vary from distinct and deep to obsolete. The pronotum is generally transverse and narrowed, sometimes only weakly so, towards the apex, variously margined and produced at the anterior angles. The head and pronotal punctation varies from almost obsolete to strong or there may be a mixture of sizes and this is a useful aid to identification. Elytra usually elongate and only a little, if at all, broader than the pronotum at the base, the humeral calli vary from strong to obsolete and the larger punctures are arranged in distinct rows. Front and middle legs long and slender, hind legs robust; femora strongly developed, the tibiae bear a single short apical spur but vary widely in form; the tarsal grooves, lateral curvature and dentation being useful identification aids. The hind tarsi appear articulated with a distinct angle between the first and second segment, the first segment is long and slender, often half the tibial length, a character which might suggest a Longitarsus but the 10-segmented antennae are unique to this genus in the U.K. Most species are monophagous or oligophagous and several are common and widespread in the UK The widespread and generally abundant P. chrysocephala (Linnaeus, 1758) is a notorious pest of various Brassica crops.