Thallus: crustose, composed of scattered to crowded areoles forming small patches 1.5-3.5 mm across areoles: flat to somewhat convex, rounded, angular or irregular in outline, up to c. 0.25 mm wide surface: greenish yellow to yellow Apothecia: common, lecanorine, 0.15-0.4 mm wide disc: darker yellow than the thallus, ±plane to somewhat convex margin: uneven, entire to granular to ±excluded exciple: sometimes visible from the outside, thin to thick epihymenium: yellow-brown hymenium: hyaline, 60-75 µm tall; paraphyses: simple or sometimes branched apically, cylindrical or with somewhat swollen, to 3.5 µm wide tips; hypothecium: hyaline asci: clavate, 24-32+-spored ascospores: hyaline, simple to 1-septate, oblong to ovoid, 7-12 x 4-5 µm Pycnidia: not seen Spot tests: K- to K+ reddish, KC-, C- Secondary metabolites: not investigated, probably the same pulvinic acid derivatives as in the other species of the genus. Substrate and ecology: on bark of broad-leafed trees, shrubs and conifers, often on twigs and branches World distribution: circumpolar(?) in the Northern Hemisphere Sonoran distribution: rather common in open montane forests in central and northern Arizona up to at least 2900 m. Notes: Candelariella lutella is a fairly common, but it is minute and easily overlooked species. It is characterized by its small apothecia and its small areoles forming very small yellow patches typically at the base of small branchlets or next to cracks in the bark. Candelariella xanthostigma has a granular thallus, which often forms widespread stands and mostly has larger apothecia, and C. vitellina is normally a much larger species.