Westwood placed these wasps and the POMPILIDAE in a single family, but Kohl, while separating the latter, has grouped a number that were once ranked as families, under the SPHEGIDAE, calling them simply sub-families, thus making this a much more extensive division, the SPHEGIDAE proper forming only a part of the whole. Dalla Torre in his Catalogue treats them as a sub-division of the CRABRONIDAE; but Sharp takes Kohl’s classification, which I follow. The _Sphegides_ are easily distinguished by the peculiar structure of the abdomen; the basal portion is produced into a slender rod-like stalk or pedicle, with the apical part forming a rounded or oval tip; they are very active creatures with the habits of the larger sand wasps. The world-wide Genus _Ammophila_ is represented in Australia by four described species; they make their nests in sandy ground, digging out a straight burrow with an enlarged chamber at the end, which they store with different kinds of caterpillars they capture on the plants while hunting; these they sting but do not kill, but though paralysed and incapable of motion, remain alive long enough to furnish the baby wasps with a supply of fresh food. _Ammophila suspiciosa_ is a slender black insect under 1 inch in length; the thickened tip of the abdomen is dull red. This is our common species found all over the western country. _A. instabilis_ is a larger black species with semiopaque wings and reddish legs; the tubular portion of the body and base of the thickened part are reddish brown: this one is a northern form found in Queensland. _Pelopaeus laetus_ is a very handsome black and yellow wasp with a somewhat similar shaped body tipped with black; it is very variable in size, the largest measuring about 1 inch in length. It has a wide range over Australia, and differs from the former insects in being a regular “mud dauber,” forming a regular clay nest consisting of a number of different cells, each of which is filled with paralysed spiders. It is a very friendly insect, often flying into the room on a summer day; and will build its nest on the edge of a roof or wall.