The descriptive text, below the map, is from the Cornish Red Data Book (2009). The map on this web page depicts the organisms distribution and shows the records made pre-2000 and those made since.
A southern species that has undergone a decline in Britain due to air pollution and the loss of its main habitat, wayside trees. It is still found in scattered sites from Kent west to Cornwall, and north to Northamptonshire, with outlying sites in Wales and south-west Scotland. The Lizard Peninsula sites are unusual in that the species is saxicolous and confined to the serpentine rock. The Lizard is one of the strongholds for this species.
I.J. Bennallick, S. Board, C.N. French, P.A. Gainey, C. Neil, R. Parslow, A. Spalding and P.E. Tompsett. eds. 2009. Red Data Book for Cornwall and the Isles of Scilly. 2nd Edition.Croceago Press.
The Cornish Red Data Book Project was led by the Cornwall and Isles of Scilly Federation for Biological Recorders (CISFBR). The full text and species accounts (minus the maps) are available on the CISFBR website.