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(Map updated: 11 August 2009)

This creamy-white, crustose species only a few centimetres in size occurs frequently on siliceous rocks, including man-made structures. The thallus forms a tight crust with fine cracks across the surface from which powdery soredia arise giving the surface a faintly floury appearance. A dab of C (fresh bleach) will turn it red. The species is scattered in Ireland, and possibly under-recorded.

Key characteristics

• The C+ reaction immediately suggests the genus Trapelia
• The creamy colour and slightly greener soredia help to confirm this species.

NBN Atlas mapping: Species account : NBN Atlas UK Species Observations database

iNaturalist: Species account : iNaturalist World Species Observations database

Original text submitted by Simon Davey