CHAPTER X 



THE BODY-WALL AND MUSCLES 



The Body-Wall (fig. 88). 



The Body-wall in the Dragonfly, as in other insects, is formed 

 of a strong external non-cellular chitinous cuticle, with an under- 

 lying cellular layer, the hypodermis. 



The Cuticle is not a single layer, but consists of several parallel 

 laminae, of different staining intensities. It is formed as a secretion 



Fig. 88. Section of body-wall of abdomen of larva of Synlestes weyersi Selys 

 ( x 1000). cutt darkened outer layers of cuticle; cut 2 clear inner layer of 

 same ; hy hypoderm ; m muscle-fibres ; n nucleus of hypoderm cell. Original. 



from the cells of the hypodermis. It may be quite clear and 

 transparent throughout, but is more usually pigmented with 

 black, brown or orange. The pigment is always densest in the 

 outer layers (cut-^. The layer next the hypoderm (cut 2 ) remains 

 unpigmented. The outermost layer may be either smooth or 

 sculptured, frequently by close and delicate striae. Often it is 

 covered with minute hairs or bristles, each set in a tiny depression 

 surrounded by a raised circular wall. In certain regions numerous 

 minute pores occur in it [39]. 



At various points the cuticle is turned inwards into the body 

 of the animal, forming structures designated as endoskeleton. 

 Such are the tentorium, the posterior foramen, the apodemes of the 

 thoracic and abdominal segments. At the spiracles it is also 



