The Canadian Entomologist
The wasps belonging to this family, on account of the emarginate eyes in the females, and the abdomen being usually marked with yellow or white, closely resemble those in the families Mysinidae and Scoliidae, but may be easily distinguished by the great difference in the legs, the middle coxae being approximate, the outer face of the tibiae being smooth, unarmed, without tubercles or spines, while the tarsi are without strong spines or bristles, and unfitted for digging.
Ashmead, William H., "Classification of the Fossorial, Predateous and Parasitic Wasps, or the Superfamily Vespoidea No.11" (1903). An. Paper 79.