(Müller, O.F., 1776)
This is a very widespread Palaearctic species extending from Northern France to Mongolia, including Ukraine and Crimea, and north to Scandinavia and the U.K. It occurs up to 1500m. in Bulgaria. In the U.K. it occurs locally throughout England, Wales and Southern Scotland but may be in decline; there are only older records from Ireland. Host plants include various Apiaceae e.g. cow parsley, Anthriscus sylvestris, Hogweed, Heracleum spondylium, and ground elder, Aegopodium podagraria, and the beetles are likely to be found wherever these thrive e.g. parkland, open woodland, wasteland and grassland generally. Adults occur year round; they overwinter among stones, litter or in tussocks etc. and become active during April or May when they feed nocturnally on the developing host foliage. Oviposition begins in April with eggs being deposited on tender leaves and stems, and larvae emerge in April and May. Like the adults they feed nocturnally, and develop rapidly, being full grown after three to five weeks when they descend the stems and enter the ground to construct a pupal cell. Prepupal and pupal stages last about three weeks and the first new generation adults eclose during June; this produces a peak in adult abundance as they combine with the previous generation. During hot weather the adults may be seen high up on host stems or among the flowers, possibly consuming pollen, but otherwise they are strictly nocturnal; locally we sweep the occasional specimen by day but at night we find them by torchlight, often in large numbers and gregarious on the hosts in our local park and so this would seem to be the best way to record the species.
A large and conspicuous leaf beetle, 7-9mm, entirely black and usually with a faint blue or bronze reflection although forms occur where the reflection on the head and pronotum is different to that on the elytra, and many aberrations have been named e.g. ab. lamina (Fabricius, 1791) has the dorsal surface green, ab. laevicollis Olivier, 1708 is intensely blue, ab. roscida Bechyne, 1946 has a strong coppery reflection, and ab. vieta Bechyne, 1946 has the dorsal surface entirely dull black. The antennae are entirely black but for the pale ventral surface of the two basal segments. The Pronotum is broadest at the base and narrowed to the anterior margin, the lateral margin only weakly curved, or sometimes almost straight. The surface is shiny and very finely punctured and microsculptured, the lateral grooves are sharply defined, deep and complete,
Chrysolina oricalcea ♂
Chrysolina oricalcea ♀
Chrysolina oricalcea underside
or almost so, from the base to the apex, the surface between these and the lateral margins is strongly convex and lacks coarse punctures. Each elytron has nine regular rows and an abbreviated scutellary row of strong punctures; the interstices are finely micropunctured and reticulate. Legs entirely black, usually with a metallic reflection. The terminal segment of the tarsi lack ventral teeth at the apex. The claws are dark yellow.