Chrysolina banksii (Fabricius, 1775)
The subgenus Chrysolina s.str. includes only 5 species of which 3 are Canary Island endemics, C. staphylea (Linnaeus, 1758), the type species of the genus, is Holarctic, and the present species which is western Mediterranean in distribution extending south to North Africa and north to the U.K.. There is also a population in the Himalayas. Several regional variations, sometimes considered as subspecies, occur; a metallic bronze-green form, chlorizans Weise, 1884 is widespread, ibezensis Bechyne, 1950 from the Balearic Islands, ausonia Schatzmayr, 1941 from central Italy and peloritana Schatzmayr, 1941 from Sicily, the nominate form is widespread and occurs in the U.K. Here it is a local species of coastal or near coastal occurrence from Hampshire to North Wales, including Anglesey and the Isle of Wight, and very local further north; there are a few central and eastern records, mostly from Essex and Kent. The typical habitat is open grassland, heaths, dunes, wooded margins and salt marsh. Adults generally occur year-round, although in severe winters they may fail to survive, overwintering in moss and tussocks etc. near the host plants and becoming active in the spring. New generation adults appear in May and June and feed for a few weeks before they aestivate during the summer, they resume feeding in September and begin oviposition soon after. Eggs are laid in small batches on the underside of host leaves; in the U.K. both adults and larvae feed mostly on ribwort plantain, Plantago lanceolata, but a range of hosts have been recorded including various Lamiaceae e.g. Calamintha ascendens, Lamium, Galeopsis, Marrubium vulgare and Ballota nigra, Asteraceae including Cynara sp. and Apiaceae including species of Foeniculum. Larvae emerge in the autumn and develop quickly, passing through four instars, before overwintering at the base of plants; they resume feeding in the spring and pupate in the soil during April and May. Although local the beetle may be common where it occurs.
A large and dark species; dark brown to bronze, with a distinct metallic reflection and pale, non-metallic appendages. 8-11mm. The head is broadly visible from above in normal setting, the eyes generally hidden within the produced anterior angles of the prothorax. The antennae are pubescent from the seventh segment, and the terminal segment of the maxillary palpi is truncate. Pronotum strongly and evenly narrowed from the base to the apex, the lateral grooves are deep and strongly, often confluently, punctured, and the sublateral suface is strongly convex. The disc is very finely punctured to impunctate. The elytra are a little wider at the base than the base of the pronotum, weakly rounded to subparallel and with scattered strong, almost foveate, punctures and sparse micropunctures. The wings are variously developed but it seems the species rarely flies. The pro- and meso-tarsi are strongly dilated in the male.
In the U.K. the only confusion might be with C. staphylea but this is generally smaller, 5-8.5mm, lacks a metallic reflection and has the pronotum more or less parallel-sided in the basal half.