I restricted looking to South facing stone but nothing evident
Lichens were not abundant on southern Faces and in particular the usual section were I think wall had been repointed and anti foul paint applied . I did however find one Caterpillar circa 0.8 - 1.1. cm. Unfortunately my usual lens is shot so the imaging on the G6 is not good
It looks like the caterpillar of The Common Footman Double Click Image Link ( ???) and Link 2 which would make sense being found at the base of Lichen Covered Wall . The second image below is lightened and trimmed and you can see (i) the 8 extended orange segments and (ii) the white bristles on each segment The larvae feed on various species of lichens found on trees and fence posts. It overwinters as a larva.