1 72 THE 1NTEGUMENTAL SKELETON OF THE IMAGO. 



and behind by the transverse ventral suture and the inter- 

 mediate coxae. 



The Entothorax (Plates VII., Fig. 2, and VIII., Fig. 4) con- 

 sists of a subtriangular vertical plate (j_?), strengthened by 

 cord-like ridges. The apex of this plate supports a saddle-like 

 meso-furca, on which the great thoracic nerve-centre lies. 



The vertical plate extends from the manubrial suture to the 

 posterior border of the plastron ; it supports a pair of capitate 

 processes behind (jo), which articulate with the intermediate 

 coxae. The horizontal furca is concave above, and supports 

 four spathulate processes, from which muscles moving the legs 

 and wings arise. 



The Great Entopleuron (29) is the inflected margin of the 

 posterior external angle of the plastron. It is a large oblique 

 plate, which gives origin or insertion to several muscles. 



The Lateral Plate. Seen externally, this plate is quadrilateral, 

 and is raised, above and behind, from the surface of the thorax 

 by its deeply inflected margins. In front it is bounded by the 



DESCRIPTION OF PLATE VIII. 



DETAILS OF THE THORACIC SKELETON. FIG. i. Anterior View of the Thorax : ja, 



smooth surface on the prescutum ; pd, prodorsum ; j 1 , sella ; s", manubrium ; / : 



and/-, greater and lesser pectorals ; c l , condyle, with the claviculre below. 

 FIG. 2. The same seen from behind. 

 FIG. 3. -The Sella and Corniculre. 

 FIG. 4. The Lower Part of the Thorax seen from above : aa', part of the first 



abdominal ring. 

 FIG. 5. The Thorax, with the Abdomen removed, seen from behind : / d, post 



dorsal arch ; t p, tympanic plate. 



FIG. 6. The Posterior Extremity of the Median Part of the Metasternum. 

 FIG. 7. The Pleuron seen from outside : hp, hypopterygium ; ha, hamulus ; epc, 



epicosta ; f, lower extremity of the fissure in the ascending process. 

 FIG. 8. The Internal Surface of the Pleuron : a, extremity of the tympanic ridge; 



sac, sacculus ; l>, spines forming ridges on the inner surface of the thoracic wall. 

 FIG. 9. The parapteron and its relations, seen from the Interior of the Thorax : 



a, anterior process ; sd, part of the mesopleural syndesmosis ; b, long process ; 



pe, pre-epaulet ; hp, hypopterygium ; ha, hamulus. The wing and sacculus have 



been removed. 



FIG. 10. External Surface of the Metapleuron. 

 FIG. it. The Internal Surface of the same : ap, apodeme of the halter ; a 1 , part of 



the first abdominal segment ; r, ridge between episternum and epimeron ; x, rail 



on which the hook of the posterior coxa slides. 

 The other references to the figures in this plate are the same as in Plate VII. 



