[Illustration: FIG. 57.—Transverse section of skeleton of metathorax of _Goliathus druryi_, seen from behind: _a_, metanotum; _b_, metasternum; _c_, phragma; _d_, entothorax (apophysis or furca); _e_, apodeme; _f_, tendon of articulation. (After Kolbe.)] The appendages of the thorax are (_a_) inferior, the legs; (_b_) {104}superior, the wings. The legs are always six in number, and are usually present even in larvae, though there exist many apodal larvae, especially in Diptera. The three pairs of legs form one of the most constant of the characters of Insects. They are jointed appendages and consist of foot, otherwise tarsus; tibia, femur, trochanter, and coxa; another piece, called trochantin more or less distinctly separated from the coxa, exists in many Insects. The legs are prolongations of the body sac, and are in closer relation with the epimera and with the episterna than with other parts of the crust, though they have a close relation with the sternum. If we look at the body and leg of a neuropterous Insect (Fig. 58) we see that the basal part of the leg—the coxa—is apparently a continuation of one of the two pleural pieces or of both; in the latter case one of the prolonged pieces forms the coxa proper, and the tip of the other forms a supporting piece, which may possibly be the homologue of the trochantin of some Insects. In some Orthoptera, especially in Blattidae, and in Termitidae, there is a transverse chitinised fold interposed between the sternum and the coxa, and this has the appearance of being the same piece as the trochantin of the anterior legs of Coleoptera. [Illustration: FIG. 58.—Hind leg of _Panorpa_: _a_, episternum; _a′_, epimeron; _b_, coxa; _b′_, coxal fold of epimeron; _c_, trochanter; _d_, femur; _e_, tibia; _f_, tarsus.]