The grey forewings are crossed by jagged cross-lines and bands. The red hindwing which gives it the English name has a black band around the scalloped margin, fringed with white. Another irregular black band runs across the centre of the red patch of the hindwing.
The larvae can be found from May to July feeding at night and hiding under loose bark or in a crevice during the day. They overwinter as eggs.
Size and Family
- Family – Catocalinae (Noctuidae)
- Large Sized
- Wingspan – 66-80mm
Conservation status
- UK BAP: Not listed
- Common
Caterpillar Food Plants
Black-poplar (Populus nigra), White Poplar (Populus alba), Aspen (Populus tremula), other poplars and willows.
Habitat
Woodland, parkland, scrub, riverbanks and gardens.
Distribution
- Countries – England, Wales, Scotland and Ireland
- Common and well distributed in central southern and south-east England, in the Channel Islands, East Anglia, Lincolnshire, the Midlands and east Wales. More local in south-west England, west Wales, northern England to Cumbria and on the Isle of Man.

Red Underwing - Iain Leach
Red Underwing
Iain Leach

Red Underwing - Iain Leach
Red Underwing
Iain Leach

Red Underwing - Garry Barlow
Red Underwing
Garry Barlow

Red Underwing - Mark Joy
Red Underwing
Mark Joy

Red Underwing - Stuart Read
Red Underwing
Stuart Read
