The two great divisions of the body—the mesothorax and the metathorax—are usually very intimately combined in winged Insects, and even when the prothorax is free, as in Coleoptera, these posterior two thoracic rings are very greatly amalgamated. In the higher forms of the Order just mentioned the mesosternum and mesopleuron become changed in direction, and form as it were a diaphragm closing the front of the metasternum. The meso- and meta-thorax frequently each bear a pair of wings. We have described briefly and figured (Fig. 55) the sclerites of the mesothorax, and those of the metathorax correspond fairly well with them. In addition to the sclerites usually described as constituting these two thoracic divisions, there are some small pieces at the bases of the wings. Jurine discriminated and named no less than seven of these at the base of the anterior {103}wing of a Hymenopteron. One of them becomes of considerable size and importance in the Order just mentioned, and seems to be articulated so as to exert pressure on the base of the costa of the wing. This structure attains its maximum of development in a genus (? nondescript) of Scoliidae, as shown in Fig. 56. The best name for this sclerite seems to be that proposed by Kirby and Spence, tegula. Some writers call it paraptère, hypoptère, or squamule, and others have termed it patagium; this latter name is, however, inadmissible, as it is applied to a process of the prothorax we have already alluded to. [Illustration: FIG. 56.—Head and thorax of wasp from Bogota: _t_, tegula; _b_, base of wing.] To complete our account of the structure of the thorax it is necessary to mention certain hard parts projecting into its interior, but of which there is usually little or no trace externally. A large process in many Insects projects upwards from the sternum in a forked manner. It was called by Audouin the entothorax; some modern authors prefer the term apophysis. Longitudinal partitions of very large size, descending from the dorsum into the interior, also exist; these are called phragmas, and are of great importance in some Insects with perfect flight, such as Hymenoptera, Lepidoptera, and Diptera. There is no phragma in connection with the pronotum, but behind this part there may be three. A phragma has the appearance of being a fold of the dorsum; it serves as an attachment for muscles, and may probably be of service in other ways. More insignificant projections into the interior are the little pieces called apodemes (Fig. 57, _e_); these are placed at the sides of the thorax near the wings. The apophyses are no doubt useful in preserving the delicate vital organs from shocks, or from derangement by the muscular movements and the changes of position of the body.