Caloplaca arcis


A tiny, bright yellow or orange-tinted Caloplaca that forms rosette-like clusters of areoles, minutely squamulose or lobed at the margins and bearing spherical blastidia up to 0.1mm across; apothecia with yellow-orange discs, thalline margins generally persistent.

It reacts to K turning crimson.

Identification difficulty
Recording advice

Unless identified by a recognised expert, a photo is required and the specimen should be examined with a microscope. In the comments box, state the key or ID method used and describe the size and identifying characters.


On walls and in churchyards.

When to see it

All year round.

UK Status

Widespread and locally frequent.

VC55 Status

Status in Leicestershire and Rutland not known.

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Leicestershire & Rutland Map


Yellow squares = NBN records (all known data)
Coloured circles = NatureSpot records: 2020+ | 2015-2019 | pre-2015

UK Map