The Genus _Diplax_ contains a number of more delicate, short-winged insects, of which _Diplax rubra_, a typical form, is common both along the rivers and in the open scrub, often quite a distance from water. It is a moderate-sized dragon fly, tinted with pale yellow at the base of the hind wings, and has a distinctive bright red body. _Diplacodes (Diplax) bipunctata_ has much the same habits, and a wider range over the country; it is common about Sydney, and is slightly smaller than the previous species, and of a general yellow tint. _Orthetrum nigrifrons_ is a more thickset dragon fly about 2 inches across the wings; the head and front of thorax are black, with the hind portion of the latter and body deep blue; it is a very distinctive species along the watercourses and in the open bush. _Orthetrum villosovittatum_ is a slightly larger form found in Southern Queensland, with slightly clouded wings, blotched close to the body with yellowish brown: the head and thorax are brown, and the body is red. * * * * * The AESCHNIDAE contain the giants among the dragon flies: _Petalura gigantea_ is our largest species, and varies much in different localities; most of ours on the Blue Mountains measure about 5 inches across the wings, but Tillyard captured them at Cairns N.Q. 6½ inches. It is a very robust insect of a dull brown tint, with a single, broad, pale stripe on the sides of the large square thorax, and when viewed from the side seems to have the abdomen attached to the under-side of the thorax. The pterastigma of the wing is long. _Hemianax papuensis_ is typical of one of our large species, often flying in numbers about Sydney hawking for gnats high up in the air before a storm. It measures 4 inches across the wings, which have a slight smoky tint. _Aeschna brevistyla_ is about the same size as the previous species, but the wings are clear, and the abdominal segments are marked with two angulated white blotches, one on either side of the dorsal stripe. The larvae are curious, elongate, oval creatures, with large heads, living in the mud at the bottom of stagnant ponds and are common about Sydney. * * * * *