The Brazilian solifuge Mummucia mauryi new species (Solifugae, Mummuciidae) from sand dunes of the São Francisco River, in semiarid caatinga domain, is herein described, with illustrations of the main taxonomic characters. This is the first species of Solifugae described from the Brazilian caatinga. The specimens were collected in pitfall traps during both the rainy and dry seasons. It exhibits diurnal activity and a clumped distribution (Morisita's index = 3.32 and 1.38 for rainy and dry season, respectively). Sun-exposed areas were avoided during the dry season, when preference for the cactacean Opuntia inamoena was detected. We suggest this association is related to predator avoidance.