NO. 3 INSECT HEAD SNODGRASS II3 



(figs. 41, 44, J5, S4' 3^^ 41) function in connection with the mouth. 

 The dorsal dilators {33, 34) arise upon the clypeus (fig. 41, Clp). 



The true pharyngeal region of the stomodeum of the grasshopper 

 is differentiated into an anterior pharynx and a posterior pharynx, 

 the two parts being thus named by Eidmann (1925) in the roach. 

 The principal differences between the two parts of the pharynx, how- 

 ever, are in the conformations of the cuticular lining, though the 

 posterior end of the anterior pharynx is marked externally by a slight 

 bulging of the lateral walls. The circumoesophageal connectives (fig. 

 44, CoeCon) lie approximately between the two pharyngeal sections. 



The crop (fig. 43, Cr) is a large, rather stiff-walled sack, represent- 

 ing probably both oesophagus and crop in insects with a long oesoph- 

 ageal tube, though the posterior section of the pharynx in the grass- 

 hopper appears to be the oesophageal region in the caterpillar (fig. 

 55). The anterior end of the crop in Dissosteira lies in the back of 

 the head where it rests upon the bridge of the tentorium (fig. 41) : 

 the ventral surface of the thoracic part of the organ is supported by 

 the spreading apophyses of the thoracic sterna. The anterior third of 

 the crop (fig. 43) is somewhat set off from the rest by a slight nar- 

 rowing of the walls ; the posterior part tapers between the large 

 anterior caecal pouches of the ventriculus, and ends in the proventric- 

 ulus (Pvent). The proventriculus is a small, cup-shaped enlarge- 

 ment of the posterior end of the stomodeum, mostly concealed between 

 the bases of the ventricular pouches (GC). 



The frontal ganglion of the stomodeal (stomatogastric) nervous 

 system (fig. 43, FrGng) rests against the anterior wall of the pharynx, 

 and the posterior median oesophageal ganglion (OeGng) lies over 

 the posterior end between the spreading bases of the last pair of dorsal 

 dilator muscles of the pharynx (j/). From this second median gan- 

 glion a long lateral nerve {LNv) goes posteriorly on each side of the 

 crop, ending on the rear part of the latter in a posterior lateral gan- 

 glion (PLGng). A pair of short anterior lateral nerves from the 

 oesophageal ganglion go laterally to a pair of globular bodies, possibly 

 the corpora allata (CA) , lying at the sides of the posterior pharynx. 

 The anterior dilated end of the aorta (Ao) rests upon the oesophageal 

 ganglion, and its open, trough-like lower lip is extended forward be- 

 neath the brain. 



The Inner Wall of the Stomodeum. — The surface of the intima, or 

 cuticular lining, of the pharynx, crop, and proventriculus is diversified 

 by various folds and ridges, most of which are clothed with hairs or 

 are armed with small chitinous teeth. 



