Golden-bloomed longhorn beetle

Occasionally, we delve into our species lists for a closer look at some of the reserve’s more unobtrusive and less fluffy residents. Today it’s the turn of the golden-bloomed longhorn beetle (Agapanthia villosoviridescens), first identified and photographed by our wildlife photographer, Simon Knight, in the summer of 2020.

This is a large and very distinctive beetle with a golden iridescent bloom on its wing cases and enormously long, downward curving antennae, banded in black and white, the whole colour scheme reminiscent of a Belisha beacon. It likes our moist meadows and hedgerows where the adults spend the summer feeding on hogweed, cow parsley, and nettles.

Golden-bloomed Grey Longhorn beetle by Brian Tomlinson (CC BY 2.0) flickr.com

Golden-bloomed longhorn beetles are stem borers. The adult female gnaws a hole in the hollow stem of one of many different species of plants, lays a single egg there and seals it in. The larva develops inside the stem of the host plant, mining its way downwards as it grows. It builds a pupal cell near ground level, where it overwinters. The new adult emerges in the spring through an exit hole cut in the side of the stalk.

This beetle is fairly common in the south and east of England but its life-cycle is particularly sensitive to management regimes. If its larva’s host plant is cut down before September, the larva will be killed; if the host plant is cut too close to the ground after September, leaving a stub less than 10cm high, the pupa will die. Our habit of clearing away our gardens’ dead flower stems at the end of the summer may cost us more than we think.

Belisha beacons © identity chris is (CC BY-NC-SA 2.0) flickr.com

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