Mutillid wasps are active and conspicuous insects, but their interactions with each other and with other animals are seldom observed. Mostly indirect evidence is used to postulate that an array of traits represents adaptations to exploit ground-nesting, aggressive, often highly dispersed hosts. The massive exoskeleton protects the parasitoid invading nests of biting and stinging hosts; certain unrelated parasitoids attacking the same hosts are similarly armored. Female aptery occurs in mutillids and in many other wasps attacking soil-dwelling hosts. In at least two mutillid lineages, female aptery apparently led to phoretic copulation, which led in turn to selection for large size in males. Hosts are often highly dispersed and vulnerable for only a short time; this mandates prolonged searching in exposed habitats, which may have selected for a long life span and a remarkable defensive repertoire, including a powerful sting, warning squeaking, membership in mimetic complexes of warning coloration, chemical deterrents, and a variety of evasive tactics.
"Review of Adaptations of Velvet Ants (Hymenoptera: Mutillidae),"
The Great Lakes Entomologist, vol 21
Available at: https://scholar.valpo.edu/tgle/vol21/iss1/1