A Red Data Book species, in ancient oak woodland in parts of New Forest, also appearing as a migrant in the south, a priority species under the UK Biodiversity Action Plan. Historically confined as a breeding species to the New Forest in Hampshire, the early 21st Century has seen a range expansion presumably fuelled by climate change, and dispersing and migrant individuals are now recorded well away from traditional population centres. Now regularly recorded in the Test valley around Harewood Forest. Wingspan 58-78 mm. The most likely confusion species are
Red Underwing C. nupta and
Light Crimson Underwing C. promissa, which see for differences. Larva feeds on Pedunculate Oak and Sessile Oak, over-wintering as an egg.