Moths in the Cossidae family

goat moth caterpillar

Cossidae

There are 700 species in the world, but just three species of Cossidae in the British Isles. As adults the Cossidae do not have functional proboscis. They have long wings that are held like a steeply pitched roof over the body. The adults are nocturnal. The females lay their eggs in the stems of the host plant - always woody. The larvae feed in the wood and usually take at least a year before pupating.

Cossus cossus, the Goat moth (left)

The eggs are brown, and laid on the bark of ash, elm, willow, oak, birch, apple and poplar.

The caterpillar feeds on the inside of the trees. It takes three or more years of feeding on this low-quality food before it can pupate.

During the cold winter months it makes a kind of nest for itself and rests out the winter. When fully grown it can be up to 100 mm long. It gets its name from the rather unpleasant smell the caterpillars have.

It exits the tree to pupate in the ground making a hole as large as 20 mm in diameter.

The adults have a wingspan of 60-80 mm and and both front and rear wings are the same colour. They fly in June and July, usually around the food plant trees, and the females are larger and fatter than the males. It is found throughout the UK, but is more common in the south, in Europe and eastwards as far as central Asia.

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