This group is well represented in Australia, and widely distributed over the country; about 60 species have been described: several collected by Sir Joseph Banks in 1775 were described by Fabricius; Smith, in the Catalogue previously noticed, in a series of papers between 1862–69 in the Transactions of the Entomological Society, other Journals, and a British Museum publication (New Species of Hymenoptera 1879) published after his death, has described most of our species; Saussure in the Hymenoptera of the Reise Novara; and later Kohl has enriched our list. [Illustration: =Fig. 53.=--_Salius (Priocnemus) bicolor_ (Fabr.). Large sand-burrowing wasp, that attacks cicadas. (“Agricultural Gazette,” N.S.W.)] The typical genera _Pompilus_ and _Salius_ comprise a number of large yellow and black wasps with coloured wings tipped with black. They have long legs well adapted for running over the ground, and may be seen any warm sunny morning hunting about for spiders, with their antennae and wings constantly on the move as they rush about. They will attack the largest spider whether on the ground or hidden in a tree trunk; one large black undetermined species even ventures down the nests of the Trap-door Spiders and drags them forth. Sometimes one of the larger ground spiders shows fight, and it becomes a duel to the death, the wasp now and then being captured by its intended victim. They often place the spider in any suitable cavity with their eggs, but others form extensive burrows in the soil. _Salius (Priocnemus) bicolor_ is one of our largest yellow and black species, often measuring 2 inches across the wings, but variable both in colouration and size. She forms a burrow as large as a mouse hole, several feet in length, with quite a large mound of excavated soil outside the entrance; when emerging from the chamber she looks a most formidable creature, but unless captured never attempts to attack anyone. She sometimes stores her nest with cicadas many times larger than herself, which she rides down to their tomb before they are quite dead. The young larva is usually attached to the cicada’s breast when hatched out; but I have never been able to keep any alive after being dug out of the nest. This wasp has a curious habit of flying round and dragging a cicada off a branch when it is sucking up the sap; taking its place, she calmly stands over the spot and drinks up the sap that exudes from the puncture the dispossessed cicada had made in the bark. The members of the Genus _Pepsis_ are large black wasps with a beautiful metallic lustre on the wings; they are chiefly confined to the tropics, but Saussure has described one species, _P. australis_, from this country. Family 18. Smaller Sand Wasps. SPHEGIDAE.