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.
On nutrient-rich bark of old trees, Elm Ulmus spp., Ash Fraxinus excelsior , Beech Fagus sylvatica , and Ivy Hedera helix , usually near the coast. A rare and declining species confined to the extreme south of England, it has suffered greatly from the loss of Elm trees to Dutch Elm disease. Relatively large populations have recently been found, on a variety of tree species, on the Lizard Peninsula.
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.