The typical cockroach is a shield-shaped insect, with stout horny plates covering both the dorsal and ventral surfaces of the thorax and abdomen. The head, tucked under and hidden, when viewed from above by the rim of the prothorax, is furnished with two large compound eyes placed well in front; in some groups there are also two ocelli; the antennae springing from below the eyes are very long and slender, composed of a great number of short ringed segments. The jaws are well adapted for their vegetarian habits, though some among the domestic species are almost omnivorous in their tastes. Tepper considers that several species destroy the grubs and caterpillars of injurious cut-worms, but this wants further confirmation. Their legs are long and stout, covered with spines, and in the species living under stones and logs the legs are usually thickened. Many species are provided with two pairs of stout membranous wings, while the front pair (elytra) are thickened, opaque and coarsely veined; the hind wings, though frequently small, are fan-shaped, membranous and well adapted for flight. The cockroach is one of the most ancient of insects, and roaches are common in fossil beds both in Europe and America, many of them allied to our still existing forms. The female has a curious habit of carrying her keeled egg capsule protruding from her abdomen for some time before she deposits it in a suitable situation. A number of cosmopolitan species might be called domestic insects as they are only found about houses or the haunts of man; in London _Blatta orientalis_ is commonly known as the “black beetle,” swarming in cellars and kitchens. In Sydney the large yellow roach that comes flying round the room to the light is _Periplaneta americana_, an introduction from America, which has almost driven the smaller indigenous _Periplaneta australasiae_ out of our houses; while in some of the southern and eastern States of America our Australian roach has been introduced and become the common domestic pest. The little German Roach, or “Croten Bug” of America, _Phyllodromia germanica_, is sometimes found about the Sydney wharves. Many of these bush and household roaches are provided with glands at the tip of the abdomen, from which they can discharge (when disturbed) a foetid odour as a means of defence. The cockroaches are a very extensive family; Marlatt estimates that at least 5,000 occur all over the world; about 212 species are given by Kirby (Catalogue Orthoptera vol. I. British Museum 1904) as Australian. Most of our typical forms are wingless, and live under rotten logs or stones; some of the largest species are to be found in the dry interior.