Thallus: areolate, often large, (1-)4-15(-20) cm in diam., several specimens often growing adjacent to each other, (0.2-)0.4-1(-1.5) mm thick areoles: angular to sometimes round or irregular, flat to convex, rarely concave, often fertile, (0.3-)0.6-1.5(-2.2) mm in diam., contiguous prothallus: indistinct or thin, at the thallus edge, black to blue-black, rarely with a white outer margin, 0.1-0.3(-0.7) mm wide surface: light to dark red-brown to brown, in shaded habitat brown-gray to green-gray or gray; areoles sometimes with white spots or white edge, ±shiny, rarely dull upper cortex: (25-)35-80(-100) µm thick, upper part (20-70 µm thick) with crystals, cells 5-7 µm in diam.; cortex covered with an epinecral layer (2-)10-40(-45) µm thick photobiont: chlorococcoid, cells ±round, 5-22 µm in diam. Apothecia: aspicilioid, often numerous, (0.1-)0.4-1.0(-1.6) mm diam., 1-2(-5) per areole, round to angular or sometimes irregular disc: black, concave to flat, sometimes convex, sometimes with a thin ±white pruina thalline margin: usually flat, sometimes elevated, ±prominent, often white to gray and lighter than thallus exciple: I- or partly I+ blue, (10-)30-60(-90) µm; uppermost cells brown, ±globose, 5-6(-7) µm in diam. epihymenium: brown, sometimes olive-brown or rarely olive, with ±crystals, N+ green, K+ brown hymenium: hyaline, I+ persistently blue, (130-)140-210(-280) µm tall paraphyses: moniliform, with (2-)4-8(-10) upper cells ±globose, 4-6 µm wide, in lower part (1.5-)2-3 µm wide, not or slightly branched and anastomosing subhymenium and hypothecium: pale, I+ persistently blue, together 30-70(-120) µm thick asci: clavate, 90-130 x 20-37 µm, 8-spored ascospores: hyaline, simple, ellipsoid, rarely subglobose, (14-)20-31 x 11-17(-21) µm Pycnidia: usually common, 1-3(-10) per areole, immersed, often with a white rim, sometimes aggregated in ±branched formations (up to 700 µm in diam.), 130-350 µm in diam., with a black, punctiform to sometimes elongated ostiole, 50-110(-200) µm in diam. conidia: filiform, (16-)20-31(-35) x 0.6-1.0 µm Spot tests: cortex and medulla I- K+ red, P+ orange, C- Secondary metabolites: norstictic acid, usually also with trace of connorstictic acid. Substrate and ecology: on siliceous rock, often one of the dominant species on ±exposed boulders and rocky outcrops in open situation, in mountains, valleys, open woodland, chaparral or grassland, sometimes also in more shaded habitat as gorges (in San Jacinto Mountains) World distribution: northern California to Baja California Sonoran distribution: southern California and northern Baja California, at 250-2100 m. Notes: Aspicilia cuprea is a common and characteristic species of the interior valley and western mountains of California. It is a large species, with a red-brown to brown thallus color, which becomes lighter (green-gray to gray) in shaded situation. The apothecia are rather large, and the thalline margin is usually white or gray in bright contrast to the dark disc of the apothecia. It is further characterized by its brown epihymenium, its tall hymenium, its moniliform paraphyses and large spores. Its pycnidia are usually abundant, and its long, filiform conidia make the species easy to identify in the microscope. The thallus contains norstictic acid. The variance in color of the thallus, from red-brown or brown (exposed habitat) to green-gray or gray (shaded habitat) seems to be a modification due to the environment. DNA studies support this conclusion (four specimens analyzed; Owe-Larsson 9097, 9112, 9162 & 9166). The European species Aspicilia reticulata Rehm has a color rather similar to A. cuprea and also contains norstictic acid, but differs by having short conidia (6-9 x 1 µm; type specimen studied). The long conidia also distinguish A. cuprea from other brown, K+ yellow to red Aspicilia-species in the Sonoran area, as A. anglica, A. knudsenii, A. olivaceobrunnea, A. pacifica and A. santamonicae.