Rock Pimple

Willeya diffractella is a species of saxicolous (rock-dwelling) crustose lichen in the family Verrucariaceae. This lichen forms thin, crusty patches on rocks that break into small polygonal pieces, ranging in color from yellowish to olive or brown. It is found throughout eastern North America, from New England south to Alabama and west to Minnesota, growing on both limestone and non-limestone rocks. The species has had a complex naming history, being moved between different genera multiple times...