The three families, Thynnidre, Myrmosidre and Mutillidre have never been properly defined, or characterized, and their genera, at present, on account of the diversity between the sexes, and the diffi-culties attending their proper correlation, are in utter confusion, and often wrongly placed. This confusion is also due, to a certain extent, to a lack of sufficient study, and the careless and insufficient characterization of some of the species and genera by the original describers, so that until lately it has been impossible to bring them into anything like order.
Ashmead, William H., "Super-Families in the Hymenoptera and Generic Synopses of the Families Thynnidae, Myrmosidae and Mutillidae" (1899). An. Paper 72.