The male coccid is a delicate fragile little creature, usually microscopic in size, so that, unless bred out in confinement from scale-infested foliage, they are seldom seen. He has a well defined head rounded behind, furnished with moderately long antennae composed of thickened irregularly-jointed segments fringed and surmounted with fine filaments. The globular black eyes stand out on the sides of the head, but the mouth is aborted so that it cannot feed. The thorax, lobed on the dorsal surface, is furnished with a pair of rounded wings each with a simple central nervure, but he can fly well in spite of their delicate structure. The slender legs are simple, terminating in rudimentary hooks; the elongated abdomen is distinctly segmented and furnished at the extremity with a pair of long slender white filaments. This period of his existence is short: thousands of them perish very soon after they leave their scale, and the survivors as soon as they have impregnated the female die. The female coccid as soon as she settles down to suck up the sap develops under her protective shield (which, unlike the male, she never leaves) into an oval or rounded yellow mass: her legs, antennae, and even head become aborted though the segments of the abdomen are well defined in most species, and finally she becomes simply a sack of eggs. She deposits her eggs under the protection of the shield, in other cases the larvae develop within her shrunken dead skin. The larvae swarm out and spread over plants when, owing to their immense numbers sucking up the sap with their sharp beaks, they soon injure the tissue and often kill the food plant. Thus from an economic point of view the scale insects are one of the most important groups of the insect-world that man has to deal with, and thousands of pounds are spent in spraying and fumigating cultivated trees to destroy these pests. Many species are cosmopolitan in their range and choice of food plants, having been introduced all over the world, but Australia has a great number of indigenous species, many remarkable for their curious habits, particularly those forming solid woody galls on the eucalypts. The classification of the scale insects is based chiefly upon the structure of the adult female coccid, viz.:--Of the spinnerets, abdominal cleft, lobes, spines, and anal ring of the abdomen, and the structure and number of joints of the antennae. The shape and structure of the puparium or scale, or other secretions are used to separate them into the larger sub-divisions.