Chrysolina cerealis (Linnaeus, 1767)
The only member of the subgenus Chrysomorpha Motschulsky, 1860, this is a very widespread Palaearctic and Asian species occurring as five distinct subspecies:
C. c. cyaneoaurata (Motschulsky, 1860) from Siberia and Mongolia,
C .c. megerlei (Fabricius, 1801) from Central and Southeast Europe,
C. c. mixta (Kuster, 1844) from the European Alps and the Pyrenees and
C. c. rufolineata (Motschulsky, 1860) from European Russia, Crimea and Ukraine.
The typical subspecies, C. c. cerealis s.str. occurs in western, central and northern Europe including the U.K.
On the continent the typical habitat is forests, open woodland, meadows and mountain grassland above 600m. where it has been recorded from a range of Lamiaceae including mints, calamint, winter savory, and thyme. It has been recorded up to 1800m in the Pyrenees. In the U.K. it is a very local species with modern records from two sites in Wales; Snowdon and Cwm Idwal (Caernarvon), both of which are National Nature Reserves, although it has not been seen at the latter since 1980. The Snowdon population (estimated at around 1000 adults) may be in decline or it may always have been rare. Adults are active from April until October in mountain grassland where the host plant, wild thyme, occurs; both adults and larvae feed upon the leaves and, preferentially, the flowers. The eggs are laid towards the tips of grass stems near the host during June and larval development is rapid with pupation occurring during August in an underground cell near the base of the host. At least some adults usually eclose during the summer, and these will overwinter but it is thought that the main overwintering stage is the fully grown larva. The U.K. population is thought to be genetically distinct and is protected under schedule five of the Wildlife and Countryside Act, 1981.
Specimens vary in size from 6.4 to 9.3mm and females are on average larger and broader than males. This species is very distinctive among the U.K. fauna; the entire upper surface is patterned with several longitudinal bands of metallic green, blue, yellow and red colouration. The head is narrower than the anterior margin of the pronotum, metallic green or coppery with the frons contrasting metallic. Antennae black with metallic green or coppery basal segments. The pronotum is weakly impressed laterally and finely and evenly punctured except for a smooth median line, becoming a little coarser laterally. Scutellum triangular, finely punctured and metallic. Elytra with a mixture of very fine and moderately large punctures, the larger punctures for the most part irregularly arranged, and the surface, especially towards the apex, weakly strigose. The underside is dark blue to black, and the legs evenly dark metallic but for the pale claws.