Caloplaca atroflava

Description & Identification

This species has a thin crustose thallus, dark-grey in colour and cracked-areolate (like crazy-paving) when well-developed. Apothecia are 0.5mm diam. scattered to crowded, with brown-orange discs and bright orange margins. The wide ascospores with a broad septum are diagnostic. 

Chemical Tests: Apothecia are K+ purple, whilst the thallus is faintly K+ purple in places.

Similar Species

 Resembles forms of Caloplaca holocarpa agg.


On flint pebbles on chalk downland and on pebbles and shingle near the coast.


Europe, Africa, Asia, N&S America. Channel Islands, Hampshire.


Records from Wales

There appear to be no properly localised or recent records for this species in Wales. The BLS Atlas show a "post-1960" hectad dot for Anglesey (SH 36) and Pentecosts Gwynedd Flora cites its occurrence in three hectads of Caernarfonshire ("pre-1960") - these are SH12, SH13, SH55.  The NBN Gateway indicated records from SH13 and SH 55 but the map is misleading since the record dates given are "Recorded before 2002" and there are no other details.

Proposed Actions

UKBAP Signposting Actions:

1. Resurvey all past and present sites, and other sites on the South Downs with chalk peeble/flint nodule littered grassland and include Aspicilia tuberculosa
2. Ensure appropriate grazing levels to maintain the open nature of chalk pebble/flint grassland

Hectad Distribution in Wales/Link to full BLS map

Caloplaca atroflava

NBN Taxon Key