They frequent flowers, hovering over them like bees; and many species have the wings richly marked with black. The life history of our species is but little known, but I have bred several out of the clay nests of wasps, and two out of lepidopterous pupae (_Agrotis sp._). A European species is said to drop her eggs upon the clay nests of wasps; the newly hatched larva is furnished with a boring apparatus in front of its head by means of which it works its way through into the chamber; there it undergoes another stage of development and emerges from it with a simple sucking mouth to eat up the wasp larva. The larva of those attacking the “cut-worms,” _Agrotis_, devours the whole of the moth grub and pupates inside the chrysalid skin. The pupa is a very curious looking creature enclosed in a dark brown shining skin about ¾ of an inch long, with projecting spines on the head and extremity. The body is cylindrical with the first 7 segments furnished with a band of rasp-like spines or ridges on the dorsal surface, with which it moves round and round when touched. _Anthrax nigricosta_ is a handsome little black fly, with the head, under surface of the body, and two bands across the abdomen fringed with white down. The wings are deeply marked with black on the front margin, widest at the base. It measures about ½ an inch in length, and comes from Queensland. _Comptosia albo-fasciata_ is a large black fly shaded with fine reddish hairs on the dorsal surface of the body; the wings are brown, very long, with white tips; the body measures about ¾, and across the outspread wings 1½ inches. _Neuria quadripennis_ is a much smaller, but somewhat similar looking fly, with the dorsal surface and margins of the body more hairy; each wing is darkly clouded, with the base light, and the tip white. Both these species are not uncommon in New South Wales. _Acreotrichus gibbicornis_ is a beautiful little black fly with brown eyes; not much over ¼ of an inch long; the elongate antennae and head are clothed with tufts of black and white down; the rest of the body is enveloped in long silvery white down. _A. fuscicornis_ is of a rich violet black tint, a yellow line round the hind margin of the head, and a broader band round the dorsal margin of the thorax of a similar colour; the broad rounded abdomen is lightly banded with pubescence. These flies were taken in numbers hovering over the flowers of plum-trees in an orchard near Sydney. Family 9. Bladder Flies. ACROCERIDAE. These are very curious looking flies with such very small round heads, that at first sight one would think that they were broken off; but on closer examination the little knobs in front will be found to consist of two large eyes joining together on the inner edge, with small, 2 or 3 jointed antennae. Nothing is known about the larval habits of our species, but in Europe they are parasitic on spiders or their cocoons.