Wanted – Moth Detectives!

Adult Goat Moth

Can you help find a moth? Not just any moth, but a moth that eats trees?

If this sounds like a bizarre request, then read on.

Of the many hundreds of moths recorded in Devon and Cornwall, the Goat Moth (Cossus cossus) is one of the most elusive. In fact there are only 3 records of this moth for Devon in recent years. One of the heaviest of UK moths, the adult flies in June and July and has a wingspan of between 64-84mm. Its eggs are laid in bark crevices on various broad-leaved trees, typically willow and sallow. The larvae feed on the cellulose of the tree but will not emerge for 3-4 years, which is an unusually long period compared to most moths and is due to the slow digestion rate of its chosen food. After leaving the tree, the larvae pupate on the ground over winter before beginning the cycle again as adults.

A caterpillar in a tree crack with a Red Admiral feeding on a sap trail
A caterpillar in a tree crack with a Red Admiral feeding on a sap trail (c) Alan Watson Featherstone/Trees for Life

The Tamar Valley is a known stronghold for the Goat Moth, which favours an environment close to water. In fact it is usually found in trees which are stressed due to flooding, often at the edges of woodland in a sunny position.

Devon Moth Group is hoping to identify ‘goat trees’ in the Tamar Valley in order to learn more about, and help the conservation of, this rare species. A clue to its presence is a sap trail on the tree trunk which may attract the Red Admiral butterfly, hoverflies and some nocturnal moths to feed.

If you spot these tell-tale signs while out walking, please note carefully the position of the tree, take a photo, and email robert308price@btinternet.com

main image: Adult Goat Moth (c) Barry Henwood

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