This is a fairly large, heavy-bodied species with a wingspan of 55–68 mm. The forewings are grey with a large prominent buff patch at the apex. As the thoracic hair is also buff, the moth resembles a broken twig when at rest. The hindwings are creamy-white. This moth flies at night in June and July  and sometimes comes to light, although it is not generally strongly attracted.
The young larvae are gregarious, becoming solitary later. The older larva is very striking, black with white and yellow lines. It feeds on many trees and shrubs (see list below). The species overwinters as a pupa.
Recorded food plants
For details see Robinson, G. S., P. R. Ackery, I. J. Kitching, G. W. Beccaloni & L. M. Hernández, 2010.
- Acer - Norway Maple
- Betula - Birch
- Corylus - Hazel
- Populus - Poplar
- Quercus - Oak
- Rosa - Rose
- Salix - Willow
- Tilia - Lime
- Ulmus - Elm
Independently observed food plant: *"Fagus sylvatica f. purpurea" (observed 17/08/2014 Carmarthenshire Wales) Caterpillars had stripped nearly all leaves off a 15 year old copper beech.
- P. b. bucephala
- P. b. tenebrata
- Chinery, Michael Collins Guide to the Insects of Britain and Western Europe 1986 (Reprinted 1991)
- Skinner, Bernard Colour Identification Guide to Moths of the British Isles 1984
- South R. (1907) The Moths of the British Isles, (First Series), Frederick Warne & Co. Ltd., London & NY: 359 pp. online
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