Dark Crimson Underwing

This single-brooded moth flies between August and early September. Larvae occur on oak between April and June, and the overwintering stage is the egg (2).

The Species Action Plan for the Dark Crimson Underwing, produced as part of the UK Biodiversity Action Plan (UK BAP) aims to maintain all current populations. Proposed long-term aims include the re-introduction of this moth to two sites within the former range, and the enhancement of the sizes of all existing populations before 2010 (1). This may be aided by replanting oaks in ways that increase the size of mature oak woodlands, and by linking currently isolated patches together (1).

The generic name of the dark crimson underwing moth, Catocala derives from the Greek 'katõ' meaning below, and 'kalos' meaning beautiful. This refers to the brightly coloured hindwings of underwing moths. The specific name sponsa means 'betrothed woman' or 'bride'; this may be a reference to the gaudy underwear worn by Scandinavian brides (3). The dark crimson underwing has mottled brown to greyish forewings which provide good camouflage against tree bark, and brilliant red and black-banded hindwings which can be suddenly revealed when the moth is threatened; this often startles predators such as birds. The caterpillar is grey-brown with raised red spots from which black bristles protrude (5).

This species needs extensive areas of mature oak woodland, (1) and prefers oaks with deep furrows in the bark (4).

In the UK the dark crimson underwing breeds only in the New Forest, Hampshire. It was formerly known from Wiltshire, London (1), Kent and Sussex (2). It has been recorded from most European countries; the range extends north to Siberia and south to North Africa, but it is local or rare in many areas (1).

Classified as Rare in Great Britain (1).

The species underwent a decline in numbers during the 1970s, but has since resurged somewhat. The causes of the decline are thought to be due to widespread felling and fragmentation of mature oak woodland and replanting with other tree species (1).