The large head is immersed behind in the thorax; the front is deflexed, or even inflexed, so as to be placed in a plane at an acute angle with that of the vertex (Fig. 165); the compound eyes are placed at the sides of the head and rather widely separated; in front there are three small ocelli. Two of these are placed one on each side close to the eye between the eye and the base of the antenna; the third ocellus being in the middle just in front of the insertion of the antennae, between the edges of the margined space that usually runs down the middle of the front. The positions of these ocelli and the shape of the front and upper parts of the head are of importance in the classification of the family; the ocelli vary much in their development, being in some species beautifully clear and prominent (Fig. 166), while in others they are small, not easily detected, apparently functionally imperfect. The antennae are never very long, are sometimes compressed and pendent from the front of the head. The parts of the mouth are very large. The prothorax is much arched; it is often carinate or crested along the middle of the notum; this part is frequently prolonged backwards, forming a sort of hood over the base of the wings; the surface may be rugged or warty, forming in some species inexplicable structures; the legs are widely separated, all of them being placed at the sides of the body; the edge of the pronotum is distinct and situate close to the base of the leg; the prosternum frequently bears a large projection extending directly downwards between the front legs. The mesothorax is short, its chief sternal piece is very broad, the middle legs being very widely separated. The metathorax is larger; its sternal plate usually exhibits behind a sort of embrasure filled up by a portion of the first ventral plate. {281}[Illustration: FIG. 167.—Alar organs of Acridiidae (_Bryodema tuberculata_). A, Left tegmen; B, left wing: _ar.med_, area mediastina; _ar.sc_, area scapularis; _ar.disc_, area discoidalis; _ar.an_, anal area; _v.m_, vena mediastina; _v.r_, vena radialis; _v.r.a_, vena radialis anterior; _v.r.m_, vena radialis media; _v.r.p_, vena radialis posterior; _v.i_, vena intercalata; _v.u.a_, vena ulnaris anterior; _v.u.p_, vena ulnaris posterior; _v.d_, vena dividens; _v.pl_, vena plicata. (After Brunner.)]