Life habit: lichenicolous, in ascomata of Lecidella spp. Thallus: inapparent photobiont: absent Ascomata: distinct ascomatal structures missing, with loosely aggregated asci embedded in the hymenium of the host (not modified in shape by the infection), with indistinct peripheric hyphal structures, epihymenium, hymenium, and subhymenium; paraphysoids: usually indistinct, up to 2 µm in diam; hyphal tips above the asci: olivaceous brown, up to 5 µm broad asci: clavate, with a stipe, 25-45 x 12-20 µm ascospores: hyaline, usually (2)3(4)-septate (not to slightly incised at central septum), septum often wavy, ellipsoid to obovate, 12-17 x 3.5-5 µm, with a thin epispore Pycnidia: immersed in hymenium of the host, subglobose, 50-80 µm wide, upper parts olive brown conidia: bacilliform, 5-6 x 1 µm Chemical reactions: gelatinous matrix formed by asci and paraphysoids I+ red, KI+ blue; ascus tholus with KI+ blue ring-structure. Substrate and ecology: strictly confined to the hymenia of its host World distribution: widely distributed, from Europe, Africa (Algeria), North America, South America, and Australia Sonoran distribution: Arizona (Pima Co.). Notes: Hertel (1969) noticed a correlation between spore size and host, thus Arthonia intexta might consist of several closely related and host-specific taxa. It is also found in New Mexico and California north of the Sonoran area.