NO. 2 THORACIC MECHANISM OF A GRASSHOPPER SNODGRASS 53 



MUSCLES OF THE NECK AND PROTHORAX 



The prothoracic and neck muscles of the grasshopper are best studied 

 from the mesal plane of the body. They may be exix)sed by cutting 

 into lateral halves a s{>ecimen that includes the back of the head, the 

 prothorax, and the mesothorax. Before removing the alimentary 

 canal, a branched muscle should be observed going from the side of 

 the protergum to the crop and the gastric caeca, which is. 



SA Bs Ss 



Fig. 32. — Muscles of the neck of Dissostcira, right side, internal view. 



A, muscles extending between head and prothorax, omitting 5.?, 5.?, and 54, 

 shown in B, inserted on first cervical sclerite. B, muscles of cervical sclerites. 



Bsi, basisternum of prothorax ; c, first ridge of protergum ; Cv, neck ; icz', 

 first cervical sclerite ; 2cz', second cervical sclerite ; d, second ridge of protergum ; 

 e, third ridge of protergum ; EpS\, prothoracic episternum ; EpS2, mesothoracic 

 episternum ; g. process of head articulating with first cervical sclerite; H, head; 

 iPb, first phragma ; PoR, postoccipital ridge of head; PT, base of posterior ten- 

 torial arm ; Rd, posterior fold of protergum ; SA, prosternal apophysis ; iSpn, 

 first spina ; Ss, spinasternum ; Ti, protergum. 



46. Posterior protractor of the crop and gastric caeca (fig. 33 A). — 

 A slender, branched muscle arising on lateral surface of protergum 

 from lower end of first tergal ridge (c) just before base of tergal pro- 

 motor of coxa {62) ; branching ix)steriorly to lateral wall of crop and 

 tips of gastric caeca. 



The alimentary canal and fat tissue should now be removed in order 

 to expose the muscles in the side of the neck and prothorax, some of 

 which extend from the mesothorax to the head. Functionally there are 

 three groups of these muscles, namely, those that move the head, those 

 that move the prothorax, and those that move the fore leg. 



