Wingspan of 25-35 mm. Forewings are grey suffused with white and darker grey markings. Hindwings are white, each with a faint broad transverse line.
Newly hatched larvae are uniformly brown with a dark head. The body colour lightens as the larvae matures. Final instars are grey with a black head and a single dark stripe running along the back and a whitish line along each side. Clumps of long white hairs arise from orange warty pinacula along the length of the body.
Laid in rows to form a plaque and covered with greyish scales on twigs and small branches in the canopy.
Europe and the Middle East
Primarily oak (Quercus) and on occasion beech (Fagus), birch (Betula) and hawthorn (Crataegus).
Early instars feed together on leaves and hide in soil and leaf litter. Later instars form a communal silken nest. Feeding larvae skeletonise leaves. Mature larvae leave the tree in a line to locate a pupation site. Urticating hairs from the larvae cause irritation and allergic reactions in humans and pets.