June 2022
Golden-bloomed Grey Longhorn Beetle – Agapanthia villosoviridescens
Their long, delicate antennae and a golden sheen make these stem boring insects very attractive.
Fast facts
- Size: Up to 22mm long
- Distribution: Central and eastern England
- Seen: May to June
- Habitat: Damp meadows and hedgerows
- Food: Adults – umbellifer (Hogweed and Cow Parsley) and nettle leaves; Larvae – the soft centre of thistles and other herbaceous plant stems.
Description
They have long arching antennae (longer than their body) with black and pale-blue bands. Their pronotum (the part of the thorax closest to the head) is dark grey with three lateral, creamy-gold stripes. Their elytra (the hardened forewings that cover the wings) have dense pale grey to golden scales forming a mottled pattern and golden hairs that gradually rub off as they age.
It is one of only two UK longhorn species whose larvae develop in the stem of herbaceous plants, other longhorn species use the stems of woody plants.
Adults are diurnal (active during the day), in warm weather they can be easily spotted sitting on flowers with their antennae held high over their body. Although they are most often spotted on umbels they can be seen on a wide range of host plants.
Mating occurs during May and June and egg-laying follows shortly after. The female explores selected plant stems, occasionally stopping to chew the plant tissues, until she finds a suitable site.
Once she has chosen a spot she gnaws a hole into the plant stem and lays one, or occasionally two, eggs. She then seals the hole with chewed up plant material.
Larvae
The larvae emerge after a week or so and quickly grow to fill the central cavity. Rows of tiny bristles on their abdomen allow them to grip the stem from within and move rapidly through the plant.
They eat the plant stem working their way from teh top, down to the roots. By the autumn they will be fully grown and ready to overwinter in the base of the plant stem or rootstock.
The following spring they settle in the plant roots to pupate, which takes about a month. Unusually, their pupa are mobile and can move up and down in their hollowed-out cell that they've plugged at the ends with plant material.
Once hatched they remain in the pupal cell for another week or two before finally emerging to feed on herbaceous leaves and start breeding.
Spotting them
When to see them: April to August. Please help us to monitor changes in our local population by recording your sightings .
