Monday 1 February 2021

Aspicilia calcarea - Big white lichen on top of limestone walls

Are you are in the centre of Settle?

Look up to Castleberg Crag. 

The big white circular patches on the south facing cliff are Aspicilia calcaria.

I would like to give this lichen  the English name: "Big white lichen on top of limestone walls"

Here is a mnemonic to learn scientific name Aspicilia 
 Aspicilia: - pronounced:
 Ass Pee Sillier.
What could be sillier than an Ass  balanced on top of a wall, or on top of a cliff?

I have  learned (January 2021) that this lichen has just had its name changed to Circinaria calcarea. So in five to ten years time when new and revised keys and books to lichens have come into common use, that is the name we will use.. and then instead of Ass Pee Sillier we can be reminded of (big - 30cm) circular patches. 

Till then, keep looking up to Castleberg and imagine the donkey perched next to the flagpole tottering above the crag:
Ass Pee Sillier.  

Climb up through "Settle's town park" to the foot of the Crag and look at it more closely.  Next to the big white patches are medium sized (4cm) yellow patches. The yellow patches are Caloplaca flavescens .. that is for the next species)

On the cap stones on the wall at the summit you can find more Aspicilia.

Distribution map as recorded by 2020 (From the BLS website)


I think of Aspicilia as growing on hard limestone - 
(As in Craven, or the Burren, or the Alps, the Pyrenees or in the island of Öland, Sweden. In this Island scientists found that the snail Balea perversa preferred to eat Aspicilia calcarea)  But what substratum is Aspicilia growing on in SE England?

 (If you visit the Locks, Langcliffe  you can see it on the wall there: (First 30sec of video only)

Here is a description that will help a lichenologist: 

The chalky white to slightly blue-grey thallus is thin, only slightly raised above the surface of the rock.  The areoles and cracks near the edge of the thallus are arranged radially.

The margin of the thallus can sometimes be slightly lobed and has a dark grey/black margin.

 The apothecia, 0.2-1 mm of Ø (diameter), are sunken, round or angular, There are one or several apothecia per areole and are sometimes confluent. They are either black or pruinose.  The surface of the areole is sunken, but raised slightly round the rim of the areole and round the rim of the apothecium. 

This French Website for Lichens has good pictures of  Aspicilia  

This cat is interested too.
Here is some on the vertical leg of a tombstone at Horton in Ribblesdale Churchyard, with A.P. 

Left: Verrucaria fusconigrescens 
Right:  Aspicilia calcarea

Aspicilia calcarea on Clouds Pavement on the side of Ingleborough. Have you noticed how it grows especially well under the tree. This is most likely because it benefits from the bird droppings, and/or other nutrients washed down from the leaves.
"Big white lichen on top of limestone walls"
leading down to Stainforth

"Big white lichen on top of limestone walls" near Ingleton


Castleberg Crag, Settle,  as seen from the mast at Waddington quarry, 19km (12miles as the crow flies) to the south, 
(17 miles by road)   ( on Easington Fell above Clitheroe)
Taken with my Lumix TZ40.  (Not bad eh?)
So the Aspicilia can be seen from 12 miles away.

P.S. If you see a big white lichen growing on sandstone or slate it will usually not be Aspicilia calcarea.. There are several more species to choose from for acid rock.

Some website refer to it as Sunken Disc Lichen. I think that is a good name.