172 THE INTEGUMENTAL SKELETON OF THE IMAGO. 



and behind by the transverse ventral suture and the inter-; 

 mediate coxae. 



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

 sists of a subtriangular vertical plate (jj), 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 i 

 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 {2g) 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 v 

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



Descrh'tion of Plate VIII. 



Details of the Thoracic Skeleton. Fig. i, Anterior View of the Thorax : ja, , 



smooth surface on the prescutum ; pd, prodorsum ; s^, sella ; s'-, manubrium ; p^ 



and /", greater and lesser pectorals ; c^, condyle, with the claviculae below. 

 Fig. 2. — The same seen from behind. 

 Fig. 3. — The Sella and Cornicuhe. 

 Fig. 4. — The Lower Tart 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 t 



dorsal arch ; //, tympanic plate. 

 Fig. 6. — The Posterior Extremity of the Median Part of the Metasternum. 

 Fig. 7. — The Pleuron seen from outside : ///, 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 ; />, 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 ; l), long process ; 



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



been removed. 

 Fic;. 10.— External Surface of the Metapleuron. 

 Fig. II. — The Internal Surface of the same : ap, apodeme of the halter ; a}, part of 



the first abdominal segment ; r, ridge between episternum and epimeron ; .v, 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 Vll. 



