Acarospora socialis (bright cobblestone lichen) is a usually bright yellow aereolate to squamulose crustose lichen in the Acarosporaceae family that grows up to 10 cm wide, mostly on rock in western North America. It is among the most common lichens in the deserts of Arizona and southern California. It grows on sandstone, intrusive and extrusive igneous rock such as granitics, in all kinds of exposures to sunlight, including vertical rock walls. It is found in North America and Mexico, including areas of the Mojave Desert and Sonoran Desert region, to Baja California Sur. It is the most common yellow member of its genus in southwestern North America. It sometimes, but rarely, grows on other soil crusts. It is a pioneer species.