Cryptocephalus aureolus Suffrian, 1847
This widespread and generally common western Palaearctic species occurs throughout Europe from Portugal to western Russia, Asia Minor, Kazakhstan and into central Siberia, extending north into Fennoscandia, Karelia and the UK. Here it is locally common in central England south of the Wash, being almost absent from East Anglia, mostly coastal in the West Country and Wales and sporadic and generally rare further north to southern Scotland. Typical habitats include lightly grazed calcareous grassland with a rich mixture of herbaceous vegetation, especially in sites exposed to the sun such as south facing hillsides, but adults might be swept from vegetation on base-rich soils in any fairly open and dry situation e.g. roadsides and embankments, woodland and arable borders and soft cliffs along the south coast. Adults occur from April until September, peaking in June and July when they are active in bright sunshine and may be seen in numbers on various yellow flowers, especially hawkweeds, Hieraceum L. and cat’s-ears, Hypochaeris L. but also, and generally in the absence of their preferred flowers, buttercups, Ranunculus L., rock-roses, Helianthemum Mill., spotted rock-rose, Tuberaria Spach and hawkbits, Leontodon L., occasionally on white flowers of e.g. kidney vetch, Anthyllis L. and sometimes on birch foliage, they feed on pollen and may often be seen flying between flowers. Mating occurs in the spring when numbers of adults may be seen on a single plant or grouped together on a single flower, and oviposition occurs from late spring; each egg being coated with faecal matter and secretions and dropped to the ground by the female. Larvae emerge after three or four weeks, depending on the temperature, and develop through the summer, it is not known which stage overwinters but young larvae have been recorded late in the summer and so it is likely to be as larvae which complete their development and pupate in the spring.
Adults are large, 5.7-7.5mm and entirely bright metallic green, golden green or bluish green, sometimes with the forebody and elytra contrasting, on the continent many varieties or aberrations have been named based on variations in the colour of various body parts. The habitus is typical of the group; the head is hidden from above, the pronotum convex and the elytra near-parallel sided. Head coarsely punctured, with weakly convex eyes and long, filiform antennae. Pronotum broadest across acute posterior angles and narrowed to a rounded anterior margin, the lateral margins strongly and rugosely bordered, surface moderately strongly and densely punctured. Scutellum raised; obtusely angled with the pronotum in side view, quadrate, curved laterally and acutely pointed, strongly and densely punctured. Elytra with broadly-rounded shoulders and separately-rounded apical margins, widely impressed either side of the scutellum and strongly and densely punctured, the surface for the most part quite strongly rugose. The apical sternite is impressed in both sexes; in the male transversely, in the female longitudinally. Among the UK fauna only the following species is likely to cause confusion.