]00 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8l 



with levator and depressor muscles (C, D). In other insects the 

 antenna is more commonly pivoted on a ventral point of articulation 

 with the rim of the socket, as in Periplaneta (fig. 38 B, n), and thus has 

 greater freedom of movement. As already noted, how^ever, the artic- 

 ular point may be dorsal, as in Japyx, and in the Chilopoda (fig. 23 

 B, n). The thickened rim of the antennal socket (fig. 38 D, AR) is 

 braced by a short arm against the anterior margin of the heavy cir- 

 cumocular ridge {OR). A crescentic area of the head v^^all just above 

 and mesad to the antennal socket is depressed externally, and the 

 inflection tilts the place of the antennal socket somewhat dorsally, 

 giving the antenna a more upward play than it otherwise would have. 



The second basal segment of the antenna, the pedicel (fig. 38 A, 

 B, Pdc), is movable in a horizontal plane on the end of the scape by 

 means of muscles arising within the scape. The other segments of the 

 antenna are flexible but have no muscles. 



The muscles of the antenna comprise muscles inserted on the base 

 of the scape that move the antenna as a whole, and the muscles of the 

 pedicel that move the pedicel and flagellum. They are as follows : 



4. — Levators of the antenna (fig. 38 C, D). — Two muscles arising 

 on tentorium, one (D, 4a) on dorsal arm, the other {4h) on anterior 

 arm ; both inserted by a short tendon on a lobe of dorsal side of base 

 of scape (C, D). 



5. — Depressors of the antenna (fig. 38C, D). — Two muscles aris- 

 ing on dorsal arm of tentorium (D, ^a) and on anterior arm {^b) ; 

 both inserted on a long slender tendon arising near ventral margin of 

 scape (A, sAp) in articular membrane of antenna. 



6. — Extensor of the flagellum (fig. 38 C). — Arises dorsally and 

 medially in base of scape ; inserted medially on base of pedicel. 



7. — Flexor of the flagellum (fig. 38 C). — Arises dorsally and later- 

 ally in base of scape ; inserted laterally on base of pedicel. 



THE MANDIBLES 



The mandible of the grasshopper is a strongly chitinous jaw — a 

 short, hollow appendage with triangular base, thinning down to the 

 cutting margin. The anterior and the posterior angles of the lateral 

 base line carry the articular points with the head, and the apodeme 

 of the adductor muscles arise at the median angle. 



The distal edge of each mandible presents an incisor and a molar 

 area. The first (fig. 39 D, 0) forms the compressed and toothed 

 apical part of the jaw, the second (/>) forms a broad grinding surface 

 on the anterior median face closer to the base of the mandible. The in- 

 cisor and yiolar areas are not exactly alike on the two jaws, each being 



