Velvet ants (Mutillidae) are one of the largest families of solitary wasps in the Aculeata (Hymenoptera) and divided into eight subfamilies. Their larvae are ectoparasitoids of the larvae or pupae of other Aculeata, females use the sting for arresting the development of the host, as well as for defense. The sting apparatus of Mutillidae consists of the same sclerites as in other aculeates but has certain features peculiar to this family. Here, we focus on the shape of sclerites, their relative positions and articulations in representatives of some mutillid subfamilies. Some morphological adaptations are described for the first time in the subfamily Myrmosinae. The anterior bridge and 2nd valvifer articulation are apomorphic features of Myrmosinae and the coiled sting and some associated features are apomorphic for Dasylabrinae, Myrmillinae and Mutillinae. The structure and movements of the sting apparatus are discussed as well as some aspects of function evolution of the differences between the subfamilies.