Life habit: lichenicolous, parasitic, non-lichenized Ascomata: 0.2-0.4 mm in diam., in groups of 3-6 or rarely more, at first immersed and lenticular, erumpent, becoming irregular, elongated or rounded, unbranched; disc: broad, exposed, more or less plane with a thin margin, black, epruinose exciple: dark brown, closed, K-, 30-50 µm wide laterally, 25-35 µm wide at base hymenium: hyaline or pale brown, I+ red, ca. 70-80 µm tall; subhymenium I+ persistently blue; epihymenium dark brown or olive brown; paraphysoids: branched especially above, the tips brown or brownish-olive, 3-4 µm thick asci: 65-70 x 18-20 µm, 4-8-spored (Varia-type) ascospores: ovoid-oblong, sometimes ellipsoid or clavate, straight, hyaline, 3-4-septate, not or slightly constricted at the septa, 18-26(-29) x 6.5-9 µm (Parasitica-type); perispore hyaline, becoming brown granulose when over-mature, ca. 1.5 µm wide. Pycnidia: not observed. Substrate and ecology: on Lecanora rupicola group (in Europe, also reported from Protoparmelia badia) World distribution: Europe, Canary Islands, Russia, North America (U.S.A., Greenland) Sonoran distribution: Arizona (2800 m, on boulders of volcanic conglomerate at the edge of forest). Notes: Opegrapha glaucomaria is characterized by its epruinose ascomata with exposed discs, ascospores size, and occurrence on the Lecanora rupicola group.