Large (up to 50mm long) black and yellow hairy caterpillars causing defoliation of large parts of host trees. It is found on oak, hornbeam, lime, cherry, birch and many other deciduous trees and shrubs. Small trees or shrubs can be completely defoliated.

The caterpillars are present from July to October and when fully grown enter the soil to pupate. After overwintering as a pupae the adult moths emerge from late May to July.

Defoliation is most severe on small trees, however as this usually occurs late in the season it should not affect the long term health or vigour of the plants. Therefore as the caterpillars, and associated moths, can be considered part of the wildlife a healthy garden supports and should be preserved where possible. If the caterpillars are spotted early on small trees they can be removed to a larger tree. On larger trees whilst some parts of the plant may be defoliated this will have no effect on the health of the host. It is unusual for a tree to be affected in two subsequent seasons by this moth.  In addition the caterpillars, and associated moths, can be an important as a food source for other garden wildlife.