A once rare but now increasing species, associated with ancient oak woodland in parts of southern England, a priority species under the UK Biodiversity Action Plan. At the turn of the century it was very much confined to the New Forest and two large woodlands in south Wiltshire, with occasional records from elsewhere in southern England, which may have resulted from internal dispersal or migration from the continent. In Hampshire and on the Isle of Wight the 21st century has seen increasing scattered records throughout the county, still centred on the New Forest but now appearing well away from the historical locus here, likely to be a result of increased immigration from across the Channel and localised breeding in new locations. Wingspan 50-66 mm. The most likely confusion species are
Red Underwing C. nupta and
Dark Crimson Underwing C. sponsa, which see for differences. Larva feeds on Pedunculate Oak and Sessile Oak, over-wintering as an egg.