We investigated the phylogenetic structure of the velvet ant genus Dilophotopsis from sites throughout the Nearctic arid lands. The rDNA internal transcribed spacer regions (ITS1 & ITS2) were amplified and analyzed for geographic structuring. Bayesian analysis revealed two major clades; a Western clade inhabiting the Mojave and western Sonoran Deserts, and an Eastern clade inhabiting the Great Basin Desert, Chihuahuan Desert, Colorado Plateau, and the western Great Plains. Additional sub-clades found within the Eastern clade appear to be associated with specific arid lands. The geographic structuring provides insights into the processes that shaped the biota of North America’s deserts and arid lands. The deeper divergences seem to be connected to Neogene mountain building events (8-2.5 mya), while the more recent divergences are likely associated with Pleistocene climate change (2.5 mya to 10 kya). These findings are comparable to other published studies on the diversification of arid-adapted taxa.