NO. 3 INSECT HEAD SNODGRASS loy 



The walls of the salivary cup are chitinous, and its posterior inner 

 surface bears a strong chitinous keel (figs. 40 D, 41 z') projecting 

 into the interior of the labium in the base of the mentum. Two pairs 

 of muscles (figs. 40 D, 26, 2y) are attached upon the keel and the 

 walls of the salivary cup. 



The musculature of the labium is in general similar to that of the 

 maxillae. It includes the following muscles : 



i'J. — Proximal retractors of the mentum (fig. 40 D). — A pair of 

 muscles arising on ventral surfaces of posterior tentorial arms ; in- 

 serted on lateral basal angles of mentum. 



24. — Distal retractors of the menttim (fig. 40 D).^ — A pair of mus- 

 cles arising on posterior surfaces of posterior tentorial arms ; extend- 

 ing through submentum and mentum to be inserted on anterior wall 

 of labium at inner basal angles of the glossae. The distal parts of 

 these muscles are not seen in figure 40 D, being covered posteriorly 

 by muscles 2^ and 2j. The labial muscles 2^ and 24 evidently cor- 

 respond with the tentorial adductors of the maxillae (E. 12, jj). 



2 J. — Flexors of the paraglossae (fig. 40 D). — A pair of large mus- 

 cles arising in lateral basal angles of mentum ; inserted on bases of 

 paraglossae, to posterior walls, near inner ends. Each of these muscles 

 corresponds with the flexor of the galea in the maxilla (E, 16). 



The small labial glossae of Dissosteira have no muscles. 



26, 2/. — Muscles of the salivary cup (fig. 40 D). — Two pairs of 

 muscles: one pair (26) arising on basal angles of mentum, converg- 

 ing to insertions on keel of salivary cup ; the other pair (<?/) arising 

 on posterior wall of mentum near bases of palpi, converging proxi- 

 mally to insertions on sides of salivary cup. These muscles apparently 

 have no homologues in the maxillae ; perhaps they are special labial 

 muscles having something to do with the regulation of the flow of 

 saliva from the salivary duct. 



28.— Levator of the tahial palpus (fig. 40 D). — Origin in lateral 

 basal angle of mentum ; insertion on dorsal rim of base of palpus. 



2Q. — Depressor of the labial palpus (fig. 40 D). — Origin in distal 

 median angle of mentum ; insertion on ventral rim of base of palpus. 



30, 5/. — Muscles in the labial palpus (fig. 40 D). — The first (30) 

 a levator of second segment; second (5/) a depressor (adductor) of 

 third segment. 



THE PREORAL CAVITY AND THE HYPOPIIARYNX 



The intergnathal space, or preoral cavity, of the grasshopper (fig. 

 41, PrC) is of large size, but it is mostly filled by the thick, tongue- 

 like hypopharynx suspended from its roof (Hphy). Its anterior wall 



