Velvet ants (Hymenoptera: Mutillidae) are a conspicuous component of the fauna of Nearctic deserts, but little is known about their natural history. We observed a nocturnal aggregation of female velvet ants on the dune-restricted plant Croton californicus var. mohavensis (Euphorbiaceae). We collected 44 female velvet ants on or directly beneath a group of male and female plants during 2 nights. Some individuals were on flowers drinking nectar. The discovery of nocturnal velvet ants on C. californicus marks the first record of nectaring in nocturnal female velvet ants.