[1] Found only on Kangaroo Island in South Australia, it forms an intricate crust on granite rocks near the sea, providing a habitat for a diverse range of species.

[2] The Ochrolechia insularis lichen forms an irregular crust, varying in thickness from 0.3 to 4.5 mm, with a smooth, glossy, and white upper surface.

Ochrolechia insularis is morphologically similar to O. tartarea, a saxicolous (rock-dwelling) species, but differs in its smooth, glossy upper surface and lack of a prothallus.

The lichen forms part of the typical community that dominates coastal granite rocks in Southern Australia, which includes species of Rinodina, Tylothallia, Xanthoria, Buellia, Caloplaca, and Xanthoparmelia.

[2] Despite searches in similar habitats both near the type locality and further afield, such as on Flinders Island in Bass Strait, no additional occurrences of Ochrolechia insularis have been found, suggesting that this species is extremely rare and localised.