A goat in the garden?

 

A goat in the garden?

 Goat moth (Cossus cossus) June, Berkshire. 

We had a pony in the house once. It belonged to a friend of one of our daughters, but we’ve never had anything larger than dogs, cats, foxes, and squirrels in the garden.

Imagine my surprise, then, when taking the laundry off the washing line, I discovered a goat! Actually, it was a goat moth (Cossus cossus) one of just three species of the Leopard and Goat moth family (Cossidae) found in the British Isles. It is nationally and increasingly scarce, its numbers decreasing since the 1960s, but East Berkshire remains a stronghold for this species. Favoured habitats include wetlands and old woodlands.

The goat moth is one of the heaviest moths to be found in the UK and its caterpillars may be as long as 10 cms.

The adults are nocturnal and rarely seen, only flying in June and July, with the aim of finding a mate. In daylight hours, they rest on tree trunks, their livery enabling them to merge with their background. The adults cannot feed, having no functional mouth parts, and exist only to breed, living for up to two weeks after emergence.

The goat moth acquired its name because of the smell the larvae emit, which is similar to that of a male goat. The caterpillars hatch from eggs laid in crevices or on the bark of deciduous trees. They then bore into the wood, mining deep burrows. They have the longest larval stage of any British moth, taking four or five years to reach full size. During that time, they eat into the heartwood of trees, and that is one of the reasons they traditionally have been despised by foresters and gardeners.

When they reach the stage of pupation, they chew an exit out of the bark, then make a silken cocoon.

Sap and larval excrement ooze from the holes made by the larvae, providing nutrients for many invertebrates, some rare, like the Crimson Underwings moth. The sap runs attract other nocturnal moths, butterflies like the Red Admiral, beetles and some rare flies.

Not much camouflage here!

Do they serve any purpose, I wondered? The caterpillars spend three to five years developing and in that time they consume dead and decaying wood. The large caterpillars provide food for birds, bats and small mammals. Between August and October, many of the rose or magenta-coloured caterpillars leave the trees to find somewhere to create their cocoon. That is when they are likely to be seen, traipsing across the woodland floor or meandering along a path. 

Others remain on the trees where they hatched.

Goat moths are also found across Europe, North Africa, and Asia.