NO. 3 



INSECT HEAD SNODGRASS 



95 



connections. A third feature disturbing to a uniform muscle nomen- 

 clature is the fact that any muscle may break up into groups of fibers, 

 or, at least, a single muscle in one species may be represented func- 

 tionally by several muscles in another. Finally, there are muscles that 

 are evidently new acquisitions developed in connection with special 

 mechanisms. The importance of the study of musculature for the 

 understanding of the insect skeleton, however, can not much longer 

 be ignored. 



STRUCTURE OF THE CRANIUM 



The walls of the head in the grasshopper are continuously chitinized 

 on the anterior, dorsal, and lateral surfaces (fig. 36 A, B), and the 



Ant Vx ocs Oc 



Fig. 36. — Head of a grasshopper, Dissosteira Carolina. 



A, lateral. B, anterior. C, posterior. 



a, posterior articulation of mandible; Ant, antenna; at, anterior tentorial pit; 

 r, anterior articulation of mandible; Clp, clypeus ; cs, coronal suture; cv, cervical 

 sclerites ; E, compound eye ; c. articulation of maxilla with cranium ; cs, epistomal 

 suture; /, articulation of labium with cranium; For, foramen magnum ;_ /.y, 

 frontal suture; g. condyle of postocciput for articulation with cervical sclerite; 

 Gc, gena ; h, subocular ridge ; /, frontal carina ; ;, subantennal suture ; k, flexible 

 area between lower edge of gena and base of mandible ; Lb, labium ; Lm, labrum ; 

 Md, mandible; Mx, maxilla; O, ocellus; Oc, occiput; ocs, occipital suture; 

 Pgc, postgena ; Poc, postocciput ; PoR, postoccipital ridge ; pos, postoccipital 

 suture ; PT, posterior arm of tentorium ; pt, posterior tentorial pit ; sgs, subgenal 

 suture ; Vx, vertex. 



dorsal and lateral walls are reflected upon the posterior surface (C) 

 to form a narrow occipito-postgenal area surrounding the foramen 

 magnum (For). The foramen is closed below by the neck membrane, 

 in which is suspended the base of the labium (Lb). The ventral wall 

 of the head, between the bases of the gnathal appendages, is occupied 

 inostly by the large median hypopharynx, it being otherwise reduced 

 to the narrow membranous areas between the lateral margins of the 

 hypopharynx and the bases of the mandibles and maxillae. 



