12 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I42 



.'For 



Fig. 4. 



-The head of a cockroach, Periplancta amcricana, example of a general- 

 ized insect head. 



A, Anterior. B, Posterior. C, Labrum, inner surface. D, Section through left 

 side of ventral part of head, turned horizontally. 



Ant, antenna; at, anterior tentorial pit; Cb, cibarium; Clp, clypeus ; E, com- 

 pound eye; Ephy, epipharyngeal surface; For, occipital foramen; Fr, f rons ; 

 hf, fulcral point of hypopharynx ; Hphy, hypopharynx ; Lb, labium ; Lm, labrum ; 

 Md, mandible; Mth, mouth; Mx, maxilla; Oc, occiput; Phy, plmrynx; PrC, 

 preoral cavity; pt, posterior tentorial pit; SlDct, salivary diict; .9/6, salivary 

 orifice; Slv, salivarium; Tor, torma; V, ventral wall of head; Vx, vertex; y, 

 suspensory arm of hypopharynx. 



Muscles: 4, posterior muscle of labrum; 5, dilators of cibarium; 6, 7, dilators 

 of pharynx ; 13, productor of hypopharynx ; 14, reductor of hypopharynx. 



and the mandibles and maxillae on the sides. Its inner wall (F) is 

 the true ventral wall of the head, and from it arises the median hypo- 

 pharynx (Hphy). The mouth {Mth) lies anterior to the base of the 



