io8 



SMITHSONIAN M JSCi;i.LANEOUS COl.r.KCTli )\S 



VOi.. 81 



is the posterior surface of the clypeiis and labruni {Lip, Lin ). which 

 in the grasshopper is not produced into a specially developed lohe, 

 or epipharynx. The lateral walls are the inner faces of the mandibles 

 and maxillae ; the posterior wall is the anterior surface of the labium 

 {Lb). The dorsal wall of the cavity represents the true sternal region 

 of the head, sloping downward and posteriorly from the mouth open- 

 ing to the base of the labium. It is mostly produced into the large, 



Hphy 



Fig. 41. — Stomodeum, and its dilator muscles in right half of head of 

 Dissostcira Carolina. 



Clp, clypeus ; Cr, crop ; cs. epistonial suture, Fr, f rons ; Hphy, hypopharynx, 

 Lb, labium; Lm, labrum ; Mth, mouth; Fhy, pharynx; Pre, preoral cavity; SID, 

 salivary duct ; Tnt, tentorium ; v, salivary cup. 



median hypopharynx {Hphy), leaving otherwise only a narrow mem- 

 branous area on each side between the base of the hypopharynx and 

 the bases of the mandible and maxilla. 



The anterior or epipharyngeal wall of the preoral cavity presents 

 a number of features of special interest (fig. 42 A). The lateral 

 parts of the labral region of this wall are concave and fit closely over 

 the smooth, rounded, anterior surfaces of the mandibles. The bands 

 of hairs directed inward on the labral surface guard the exits from 



