Description: When sterile, this locally occurring epiphyte of north and north-west Ireland is easily mistaken for Schismatomma quercicola (described elsewhere). Like that species, the grey thallus is scattered with PD + orange-red punctiform soralia. The two species can be separated by attention to the thallus which scratches green in P. pupillaris owing to the colour of the algae, whereas in the Schismatomma (containing Trentepohlia), it scratches orange. In addition, the soralia are grey-white or yellow-white, never pinkish-grey. Furthermore, K tends to turn the thallus dirty reddish which is not seen in Schismatomma quercicola. It occurs on smooth-barked trees, especially hazel.

Key Identification Features:

• Grey thallus with punctiform soralia, grey or yellow-white coloured; K+ dirty red
• Scratches green not orange; tends to have a northern distribution in Ireland.

Original text submitted by Vince J. Giavarini

Distribution Map from NBN: Pertusaria pupillaris at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Pertusaria pupillaris at iNaturalist World Species Observations database.