Source: Hafellner J, Grube M. Arthonia epipolytropa and Arthonia subclemens, two new lichenicolous species on Lecanora polytropa, with a key to the microfungi known on this common species. The Lichenologist. 2023;55(5):241-251. doi:10.1017/S0024282923000397 - CC BY 4.0
Arthonia caerulescens (Mayrhofer 641); habitus. Scale: 0.5 mm.