The type specimen was collected by the first author in Lohja (Southwest Finland) on a high road bank northwest of a lime processing factory; there it was found growing on a pebbles that may have been enriched by calcium-rich dust.

The species epithet honours Finnish lichenologist Teuvo Ahti, "for his major contributions to lichenology".

[2] Molecular phylogenetic analysis of DNA sequences from the internal transcribed spacer regions shows that Verrucaria ahtii is closely related to V. vitikainenii.

The perithecia are partly immersed in the thallus, measure 0.15–0.32 mm in diameter, and have a dark, flat, inconspicuous ostiole (pore).

The exciple (the ring-shaped tissue layer surrounding the hymenium) measures 0.16–0.32 mm and has a dark brown wall about 13–18 μm thick.