Chrysolina hyperici (Forster, 1771)
C. hyperici is the type species of the subgenus Hypericia Bedel, 1899, a Holarctic group of about 15 species which also includes the British C. brunsvicensis (Gravenhorst, 1807). This is a widely distributed Palaearctic species; extending north through Scandinavia and Russia, south to northwest Africa and the Middle East and extensively east through Siberia. Following introductions it is now established in Australia, Canada and North America where it is used as a biological control agent to help restrict the spread of St. John’s-wort disease (Colletotrichum glocosporioides), a serious fungal pathogen that causes anthracnose and fruit-rotting disease in a range of commercially important fruit crops. In the U.K. it is locally common through southern England and Wales, becoming more sparsely and rare to the far north of Scotland, although there may have been a general decline in recent decades. Host plants are various species of St. John’s-wort e.g. Hypericum perforatum, H. hirsutum, H. maculatum and H. tetrapterum etc. and the beetles may occur wherever these thrive; parks, wasteland, woodland borders, fens and, especially, agricultural borders. The beetles generally occur in numbers but every few years there may be a population explosion followed by a few years of scarcity. New generation adults eclose from early June to late August and feed on the flowers, foliage and petioles of the host before mating begins in August and September. Oviposition begins in September and continues through the winter until February when most of the adults die off, and only a few survive into the spring. From November the adults remain among litter or in the soil, and roam the soil surface and ascend stems to oviposit during mild spells, eggs are laid singly or in small groups on the underside of leaves close to the ground, and the females are very fecund, each producing up to 2000 eggs. The larvae emerge from March or April until early summer; they feed on the foliage and growing shoots of the host and develop quickly, passing through 4 instars and becoming fully grown from June to August. Generally only 3 or 4 will feed on each shoot but in heavy infestations plants may host dozens of larvae and become completely skeletonised. Fully grown larvae descend the stems and enter the soil below the host to pupate in earthen cells a few centimetres below the surface. Adults are usually common by the end of June and remain so into the autumn.
4.8-7.0mm. Entire body black with a distinct metallic reflection, dorsal surface unicoloured bronze, reddish or green, generally with the elytra a little darker than the foreparts; several colour aberrations have been named e.g. an entirely green form, ab. viridula (Laicharting, 1781), a blue/violet form, ab. ambigua Weise, 1884, and an entirely black form, ab. privigna Weise, 1884. The appendages are entirely dark but for the claws which are at least partly yellow. Head shiny and finely punctured, with large eyes and a distinct transverse impression between the antennal insertions. Pronotum transverse and evenly curved laterally, the surface finely punctured and dull due to isodiametric microsculpture. Lateral grooves deep and entire in the basal half, becoming shallow or present only as punctures towards the apex. In ssp. daghestanica Reitter, 1912 from Iran and east Caucasus this furrow is very short and shallow. Scutellum coloured as the pronotum. Elytra finely punctured and distinctly microsculptured throughout, the larger punctures arranged in loose rows, usually some of these rows are paired to the apex, at least those behind the shoulders; otherwise they may be rather random.
Sides of pronotum finely or only sparsely punctured.
Pronotal side margins at most weakly raised.
Elytra randomly punctured all over.