Chrysolina sanguinolenta (Linnaeus, 1758)
This is the type species of the subgenus Stichoptera Motschulsky, 1860; a Palaearctic group of 12 species of which two occur in the U.K. The present species occurs from Portugal to Turkey and east to Mongolia; north to Southern Scandinavia and south to Morocco, Algeria and The Canary Islands. In the Jura Mountains it has been found up to 900m. No subspecies have been described. In the U.K. it is a rare and very local insect occurring across central southern England north to the Humber, and there are a few coastal records from the West Country and South Wales. The typical U.K. habitat is unmanaged grassland, downs, fenland and open wooded areas where the host plant, common toadflax (Linaria vulgaris Mill.), occurs although adults have also been observed feeding upon snapdragon (Antirrhinum majus). Oviposition begins in April and continues into late summer; eggs are laid on the foliage of the host and generally hatch after a week or so. The larvae develop quickly, with each of the four instars lasting about a week, and when fully developed they descend the stem and pupate in a subterranean cell; the combined prepupal and pupal stages are completed within two weeks and adults begin to eclose during May, continuing to appear through the summer and so eggs, larvae and adults may occur on the same plant. These new generation adults will overwinter among grass tussocks, moss and litter etc. and become active the following spring when they will breed, but this generation will usually die off before the next one appears. There are two peaks in adult abundance; April and May, and then again in August and September. It is thought the species is incapable of flight due to degeneration of the flight muscles despite most specimens being fully winged.
6.4-8.7mm. Distinctive due the unmetallic dark blue, purple or black colouration combined with a broad and pale, generally red, elytral margin; this margin is more or less parallel from the base to the middle and continues to the apex, it extends above and below the lateral bead and is usually visible, narrowly, in dorsal view, especially over the humeral angle. In ab. Richteri (Roubal, 1834), which does not occur in the U.K, this pale margin is absent from
the apical half of the elytra. The head and pronotum are finely punctured, the antennae black with the underside of segments two and three pale, and segments four and five are distinctly elongate. The apical segment of the maxillary palpi is quadrate with the anterior margin obliquely truncate. The pronotum is moderately transverse; the anterior margin, viewed from above, more or less evenly curved and the cuticle posterior to this flat or slightly concave. Elytra randomly and quite strongly punctured across the disc, and laterally with a distinct row of punctures within the basal half of the pale margin. Legs entirely dark, as the dorsal surface. This is distinct among the U.K. dark and pale-margined species in having an acute and posteriorly produced process behind the median lobe of the aedeagus.
Chrysolina intermedia Franz, 1938), sometimes considered to be a subspecies of C. latecincta (Damaison, 1896), is our other member of the subgenus Stichoptera. It differs from sanguinolenta in having the pale elytral border dilated towards the base, the fourth and fifth antennal segments quadrate, or nearly so, and the pronotum straighter along the anterior and lateral margins. The median lobe has a triangular projection but lacks the barb seen in sanguinolenta. This is a very local and scarce species recorded only from Orkney and Shetland and so, in this sense, should not be confused with sanguinolenta. The host plants are various species of Plantago, more especially P. maritima (Sea Plantain).