Agapanthia villosoviridescens (De Geer, 1775)
A local south eastern species with records northwards from Berkshire to Lincolnshire and west to Wiltshire. Host plants are mostly Hogweed (Heracleum sphondylium) and various thistles (Carduus spp. and Cirsium spp.) but other herbaceous plants are sometimes used: Monk's Head (Acenitum spp.), Marsh Ragwort (Senecio aquaticus), Hemp Agrimony ( Eupatorium cannabium), Mugwort (Artemesia vulgaris) and nettles (Urticae dioica). Eggs are laid into a small cavity bitten into the host stem by the female, usually only two to a plant. On hatching the larvae eats into the pith and makes its way to the base of the stem, sometimes into the rootstock. The larvae is unusual for a cerambycid, it can move rapidly within the excavated stem cavity using rows of tubercles on its dorsal surface. The pupa is also mobile, able to move up and down a pupal cell hollowed out within the stem and plugged top and bottom with fibres. Adults emerge from April and are found until October, being active on plant stems and flying readily in hot weather. The life cycle is completed within a year (Hickin).

On 07/07/07 a female was observed walking up and down a Heracleum stem, presumably ovipositing, in Cassiobury park, occasionally biting into the stem and occasionally but not always inserting its abdomen into the bitten areas, this lasted about ten minutes before the insect flew off. The stem was part of a large clump, the whole of which was heavily infested with and in many places completely covered by the chrysomelid, Phaedon tumidulus.

Readily identified from its general appearance and unlikely to be confused with any other species.

12-17mm. Antennae 12 segmented and long, reaching back beyond the elytral apex. Ist segment broadened towards apex, 2 tiny, third very long then segments becoming progessively shorter to apex. From third segment with light grey pubescence, ringed darker apically giving a characteristic appearance. First segment of maxillary palpi tapering. Head vertically inclined to body, eyes excised around antennal tubercles. Prothorax cylindrical, without borders or spines. Head and pronotum with yellow scales at sides and in a median longitudinal line above. Legs entirely black with grey pubescence. Femora without teeth, tibiae with very short spines beneath apices. Protibiae obliquely grooved on inner side. Hind tarsi as long as hind tibiae. Claws simple.

Description from 2 Watford specimens at X10