''Arthonia didyma'' is a species of
lichen
A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.[Arthoniaceae
The Arthoniaceae are a family of lichenized, lichenicolous and saprobic fungi in the order Arthoniales. The Arthoniaceae is the largest family of Arthoniales, with around 800 species. Most species in Arthoniaceae belong in '' Arthonia'' which is ...]
. It is native to Eurasia and North America.
References
Arthoniomycetes
Lichen species
Taxa named by Gustav Wilhelm Körber
Lichens described in 1853
{{Arthoniomycetes-stub