Range & Status
Recorded since 1980 in Britain only from the south, including Cornwall, Devon, Hampshire, Sussex and Kent (Waring, 1992). Common in parts of France and found in western Europe from northern Spain to Sweden (Heath & Emmet, 1983).
This species occurs at two adjacent sites in relict semi-natural ancient woodland in east Cornwall, where it was first recorded in 1856 (Clark, 1906) and also near Looe, where it was first found in 2004. The recent discovery in a previous site in Devon gives hope that it may still occur at its old site in Cornwall at Helford where it was found in 1899 (Clark, 1906). It is considered by several authors (e.g. Heath & Emmet, 1983) to be restricted to large areas of Oak forest, although the Cornish sites are small (in France, this species can be found on single hedgerow Oaks). It may be overlooked because it flies late at night. It is generally seen only in low numbers in Cornwall (Spalding, 1995b), never as commonly as in the large woodlands of Sussex and Kent.
Habitat & Ecology
The larvae feed on Oak Quercus spp. Waring & Townsend (2003) suggest that the larvae feed mainly on Pedunculate Oak Quercus robur rather than Sessile Oak Quercus petraea , which is much more widespread in Cornwall. The pupae sometimes overwinter more than once, which may give rise to apparent fluctuations in populations. The adults fly in late June.
Felling of semi-natural ancient Oak woodland, and especially its replacement by conifers.
Two of the known sites occur on woodland owned by the Forestry Commission, who are aware of the national importance of this species; the other site is a local nature reserve.