1, Costal cell; 2, median or externo-medial cell; 3, sub-median cell; 4, anal cell; 5, marginal or radial cell; 6, first sub-marginal or cubital cell; 7, second s.-m. or cubital cell; 8, third s.-m. or cubital cell; 9, fourth s.-m. or cubital cell; 10, first discoidal cell; 11, second d. cell; 12, third d. cell; 13, first apical cell; 14, second a. cell. _a_, Costal nervure; _b_, sub-costal nervure; _c_, externo-medial nervure; _d_, anal nervure; _e_, marginal or radial nervure; _f_, basal nervure; _g_, first transverso-cubital nervure; _h_, second t.-c. nervure; _i_, third t.-c. nervure; _j_, transverso-medial nervure; _k_, discoidal nervure; _l_, cubital nervure; _m_, first recurrent nervure; _n_, second r. nervure; _o_, sub-discoidal nervure; _p_, stigma; _q_, posterior margin; _r_, apical margin. (Cresson, “Hym. N. America.”)] These insects are furnished with well developed antennae; large compound eyes, in some groups composed of an immense number of facets; usually 3 simple eyes or ocelli, but these are sometimes wanting; a more or less tubular mouth adapted for sucking up food (commonly called the proboscis), though mandibles are always present. The thorax is stout and broad; the three primary portions, prothorax, mesothorax and metathorax, are distinct on the upper surface with well defined lateral or ventral plates. The legs are generally large, with spined tibiae, and slender tarsi terminating in a double claw or hook, but varying much in size and shape in the different families. The abdomen takes all kinds of remarkable forms, from the thickened sessile body of the sawfly to the slender stalked abdomen of the sand-wasp, and the female is furnished with an ovipositor, sting, or saw at the extremity. The Hymenoptera are considered by naturalists to be one of the most highly developed or specialised orders of insects, on account of the social habits of some of the chief families, and the care they display in providing for the safety and food supplies of their larvae. They undergo a complete metamorphosis: from the egg is hatched out a soft, generally legless larva which when full grown, if in a protected cell, is simply enveloped in a thin skin, but otherwise forms a stout silken or parchment-like cocoon; the larva usually takes a considerable time to change into the pupa; the change is not rapid as that of a butterfly. Australia is very rich in hymenoptera; most of the typical families are well represented, and we also have a few very distinct groups peculiar to this country.