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(Map updated: 11 August 2009)

This widespread, crustose lichen of hard upland, acid (siliceous) rock, forms white to grey patches cracked into angular islands (areoles) like evenly shattered glass. Black, mainly flat discs ranging from 0.2 to 1.8mm diam., can dominate the thallus. Thalli are K+ yellow – blood red. The lookalike L. lapicida is less neatly cracked, thinner and is K+ yellow only. L. lactea regularly grows with species such as Rhizocarpon geographicum and Schaereria fuscocinerea. Upland sites and sea cliffs; throughout Ireland.

Key characteristics

• White to grey, neatly areolate thallus with numerous black discs on acid rocks
• Thallus is K+yellow to blood-red; can form sizeable patches to five or more centimetres across.

Original text submitted by Vince J. Giavarini