A vagrant lichen is a lichen that is either not attached to a substrate, or can become unattached then blow around, yet continue to grow and flourish.^[1] Some authors reserve the expression "vagrant lichen" for those lichens that never attach, that is, those that are obligately vagrant, referring to vagrant forms of other species as "erratic lichen".^[2] Vagrant lichens generally occur in open and windswept habitats, all over the world, in all kinds of temperature zones.^[1] Habitats include saltbush (mallee) vegetation zones in Australia, steppes of Eurasia, Arctic tundra, and the North American prairie.^[1] They range from the low elevations of the Namib Desert to the high altitude Andean páramo.^[1] There are under 100 identified vagrant species, most commonly in the Aspicilia and Xanthoparmelia genera.^[1]