On the Wildside: Brown-tail moth spotted at Clumber Park

Up to three centimetres long, they are blackish with a white band down the side and covered with brownish hairs. A distinctive feature is that at the rear end of the caterpillar’s body are two raised reddish tubercles (small, rounded outgrowths). These hairs are described as ‘urticating’ which means they have an irritant effect. The hairs can be shed to cause breathing difficulties and, if in contact with the skin, rather unpleasant rashes. So overall, this discovery in north Nottinghamshire is at best a mixed blessing.

Usually active in July and August, adults brown-tail moths are white with characteristic brown hairs at the tip of the abdomens and have a wingspan of approximately four centimetres (or an inch and a half). Peter’s sighting in May seems very early and perhaps a sign of the topsy-turvy seasons. Batches of 150 to 250 eggs covered with brown hairs are laid on suitable hosts such as blackberry, hawthorn, plum, blackthorn, rose, and cherry. Hatching after around three weeks, they produce webbing whilst feeding on the foliage, but this doesn’t cause much damage to the host plant. The young caterpillars then spin dense silk nests called hibernacula, generally in exposed places like shoot tips, and this is where they will overwinter. These shelters are easily to spot in the winter, in part because they hold dead leaves which become obvious once the others have fallen.

As the weather warms in April the caterpillars once again begin to feed, but this time can result in extensive webbing and defoliation. In some areas, particularly in the south, brown-tails are abundant and may even be a public health problem. They seem to have little long-term impact on the growth of host trees and shrubs. The caterpillars pupate inside silk cocoons on the host plant during June and July, when the fresh adults emerge.

Professor Ian D. Rotherham, researcher, writer & broadcaster on wildlife & environmental issues, is contactable on [email protected]; follow Ian’s blog (https://ianswalkonthewildside.wordpress.com/) and Twitter @IanThewildside