For most species of insects, males and females appear sufficiently similar, making it easy to associate the sexes for species descriptions. Velvet ants (Hymenoptera: Mutillidae), however, have wingless females that appear extremely different from the winged males, making the association of sexes for the same species problematic. For many species of nocturnal mutillids, the females are entirely unknown, and, given their nocturnal habits, finding males and females in copulo is highly unlikely. In this study, we used DNA sequences of highly variable genes, the internal transcribed spacers (ITS1 & 2), to match unknown females with the correct species of male. This work allowed the description of previously unknown females for species such as Odontophotopsis villosa. This technique can be used in future taxonomic work to associate the sexes of other nocturnal mutillids, as well as for other groups, such as Bradynobaenidae and brachycistidine Tiphiidae, where great sexual dimorphism impedes taxonomic and phylogenetic studies.