Though these interesting little creatures were once placed in the Formicidae, and are still popularly known as “Solitary Ants” in Europe and “Cow Ants” in America, they are now classified as the first family of the fossorial wasps. Unlike the true ants, they are solitary in their habits and probably all parasitic in other insects’ nests. Until quite recently they were all placed in the Genus _Mutilla_, in which about 1,000 species have been described from all parts of the world, and about 130 from Australia; the earlier ones by Messrs. Westwood and Smith, the later ones by Andre, who has had the great advantage of obtaining a great many specimens from Mr. Gilbert Turner, who was able to sex the species, add valuable notes about their habits, and give the exact locality of the specimens collected. Turner, who was a most careful observer, after some years of collecting was not positive where they passed the earlier stages of their existence, but told me that he believed that some of them were parasitic in the nests of ants. Several of the European _Mutillidae_ are known to be parasitic in the nests of bees: I have on several occasions dug the females of the smaller species out of moss at the foot of tree trunks, and our two largest species are generally found under stones in open chambers, while on hot summer days both sexes of _Mutilla cordata_ and several other species are found running up and down the tree trunks. The males are furnished with two pairs of dark or semiopaque wings. The head is rounded; the antennae curving round; with large eyes and ocelli; the thorax broad, but showing the segmental divisions, and the abdomen rather short and rounded, without any pedicle; the legs stout, and spined on the middle pair. The whole insect is rugose and deeply punctured or roughened, and more or less clothed with pubescence and longer hairs. The females are wingless, with shorter curled antennae, very different in size, sculpture, and even colouration to the males of the same species; with the body more elongated and terminating in a long powerful sting. Andre remarks upon the brilliant metallic colouration of many of the Australian species, which is much more pronounced than in those from other parts of the world. He also says that they resemble the American species in the fact that they can be divided into two groups by the configuration of the eyes. Within the last few years specialists have subdivided the Genus _Mutilla_ into a number of new genera; and Andre places nearly all the Australian species in the Genus _Ephutermorpha_, but for simplicity I retain the old name.