Nearly all our species have been described by Smith in the British Museum Catalogue Hymenoptera 1856, and the Annals and Magazine of Natural History 1873. Under 20 species are recorded from Australia. _Bembex tridentifera_ was described by Smith from Moreton Bay, Queensland, but it has a wide range southwards to Victoria. It measures just under ¾ of an inch in length; is of a general black colour; the face yellow with a black trident-like mark above and two black spots below the antennae; the legs yellow lightly marked with black; the upper surface of the thorax spotted and barred with yellow, and the abdomen beautifully banded with irregular white bands on the 2nd to 4th segments, with the first and last only marked on the sides. _B. vespiformis_ ranges from West Australia to S. Australia, is somewhat smaller than the last, and viewed from above is black, with very faint markings on the thorax, and a broad white band on either side of the first segment of the abdomen almost meeting on the back. DIPLOPTERA. The true wasps have the antennae generally elbowed and thickened toward the tips, and the eyes notched. They have the wings folded like a fan in repose, but can fly well, and have legs and feet adapted for walking. Some species are solitary in their habits, and consist of males and females only; others live in large communities, and, like the ants, comprise males, females, and workers, the latter aborted females. Family 19. Solitary Wasps. EUMENIDAE. This group is well represented in Australia; they are well known to residents in the country from their habit of constructing clay nests under the shelter of the verandah or the eaves of the houses. They usually appear in pairs, and rapidly build up the structure, flying backward and forward with their earthen loads; from this habit they get the name of “Mud Daubers” in America, and “Mason Wasps” in this country. A number of our species are described and figured in Saussure’s “Monograph des Guepes Solitaires” published in 1851.