i;o THE INTEGUMENTAL SKELETON OF THE IMAGO. 



and 2.) To examine the anterior surface of the thorax it is 

 necessary to remove the head. This surface is then seen to be 

 subhemispherical, it consists of the prescutum and paratremata 

 above. Between the anterior thoracic foramen and the pre- 

 scutum there is a thickened rim, which is separated from the 

 edge of the prescutum by a distinct internal inflection, the pro- 

 phragma ; the ring is undoubtedly the narrow dorsal arch of the 

 prothorax. There are three smooth surfaces above the cervical 

 foramen against which the head rests, an oblong central surface 

 on the prescutum, and a circular surface on each paratreme. 

 Below each paratreme the epitrochlear sclerite (32) overhangs 

 the anterior coxa. This sclerite also articulates with the 

 posterior cervical sclerite, or condyle, which supports the head. 

 Between the condyles a small saddle-shaped sternum is seen, 

 with two remarkable processes in front covered with long 

 sensory bristles. I shall term it the 'sella' (Plate VIII., 



Fig. 3)- 



The under surface of the anterior part of the thorax is 



closed in by soft, flexible integument. This unites the neck, 

 condyles, prosternum, and anterior coxae with the meso- 

 sternum. I term it the prosternal syndesmotic area, or simply 

 the prosternal area. The integument of this region exhibits 

 several sclerites, which are perfectly distinct and movable on 

 each other in the immature imago, but become more or less 

 completely united with each other and with the mesosternum 

 in the mature insect. The sclerites of the prosternal area will 

 be more conveniently described hereafter ; their relations are 

 sufficiently indicated by the figures in Plate VIII. 



The Posterior View of the Thorax. To examine the posterior 

 surface of the thorax the abdomen must be carefully removed. 

 The thoraco-abdominal opening is surrounded by the posterior 

 coxae and a narrow process from the metasternum below, by 

 the metapleura on each side, and above by the post-scutellum. 



The post-scutellum consists of a central convex shield and 

 two somewhat triangular convex plates, one on each side, the 

 lateral plates of the post-scutellum. 



The posterior angle of the lateral plate of the post-scutellum 



