Chrysolina sturmi (Westhoff, 1882)
This is the only member of the subgenus Colaphosoma Motschulsky, 1860 and three subspecies are described; sturmi s.str. occurs in western and central Europe north to the U.K. and southern Scandinavia, ssp. diversipes (Bedel, 1892) is eastern European extending to Kazakhstan and western Siberia, and ssp. polonia (Weise, 1884), a golden-green form, occurs in Ukraine. In the U.K. it is generally uncommon and local in central southern England and very local further west and north to south Yorkshire, although there are few post-1980 records and the species may be in decline. Typical habitats are open wooded chalk downs, calcareous grassland and under cliff vegetation where the host thrives, generally exposed to the sun. Adults occur throughout the year; they overwinter among moss and tussocks etc. and become active in the spring when they may occasionally be found aggregating, following a period of feeding they begin mating and egg-laying in May. The U.K. host is ground ivy, Glecoma hederacea, on which both adults and larvae feed, but on the continent they have also been recorded from species of Galium (Rubieae) and Cirsium (Asteraceae). Larvae develop on the host from late spring but may enter a diapause during the warmest part of the year, and new generation adults occur from August. There is a single generation each year.
Among our U.K. fauna this species is instantly recognized by the size and colour; 6-10mm and bright metallic purple with the tarsi, palps and basal antennal segments pale brown or orange. The head is transverse with convex and transverse eyes that follow the outline, vertex flat and finely punctured, and the frons with a weak transverse impression. Antennae dark with two basal segments and sometimes the apices of segments 3-5 yellow. Pronotum strongly transverse with the lateral margins almost straight in the basal half; the wide dorsal margins are flat and only poorly delimited by stronger and shallow punctures, sometimes these are evanescent and sometimes more strongly impressed and confluent towards the base and apex. Disc very finely and rather densely punctured. The scutellum is dark metallic, often darker than and contrasting with the elytra. The elytral punctation is random although there is a tendency to form striae near the suture; punctures vary in size from very fine to moderately strong. Legs metallic purple with the tibial apices and the tarsi strongly contrasting pale brown or yellow. The male is shorter and proportionally broader with the apical segment of the maxillary palps and the tarsi, especially the pro- and meso-tarsi, much broader when compared with the female.