NO. 2 THORACIC MECHANISM OF A GRASSHOPPER — SNODGRASS 69 



The innermost series of lateral muscles includes two body branches 

 of the trochanteral depressor (fig. 38 A, /Jjc) which will be described 

 later. By removing the muscles attached on the tergum, there is ex- 

 posed the outer series of pleural lateral muscles pertaining to the leg 

 and wing, and the sternal muscles of the coxa. 



121. Anterior rotator of the coxa (figs. 34, 35, 38 E). — A large 

 muscle with fibers arising in two groups, one from lateral part of ster- 

 num before base of sternal apophysis, the other from sternellar lobe 

 behind the apophysis ; all fibers converge to insertions on anterior angle 

 of coxa just mesad of stalked apodeme of 118 (fig. 38 D, F, 121). 



122, I2J, 124. First, second, and third posterior rotators of the 

 coxa (figs. 34, 35, 38 E). — Origins on posterior margin of lateral arm 

 of metasternal apophysis ; insertions posteriorly on base of coxa, the 

 first (fig. 38 D, E, F, 122) on process of meral region, the second 

 {123) just within posterior angle of coxa, the third {124) on posterior 

 part of meral rim of coxa. 



The innermost pleural muscles are the large basalar and subalar 

 wing muscles (fig. 38 B, i2y, 128, I2p) ; external to them are the 

 abductors of the coxa. 



12 j. First abductor (accessory promotor) of the coxa (fig. 38 C). — 

 A small muscle arising from anterior edge of metepisternum just 

 behind and below second spiracle (2Sp) ; insertion anteriorly on ex- 

 ternal margin of coxa (fig. 38 C, D). Anatomically this muscle evi- 

 dently belongs to the abductor system of the coxa, but apparently it 

 functions as an accessory of the tergal promotor (D, 118). 



126. Second abductor of the coxa (fig. 38 C). — A large flat muscle 

 arising on inner face of episternum and on anterior surface of pleural 

 ridge ; fibers converging to insertion on slender apodeme (fig. 38 D, F, 

 126) arising in articular membrane at base of coxa just before pleural 

 articulation. 



12/. First pronator-extensor of the hind zuing (fig. 38 B). — A large 

 muscle attached dorsally on first basalar plate ( iBa) , and ventrally on 

 lateral part of sternum before coxa and laterad of base of the tergo- 

 sternal muscle (figs. 34, 38 A, 113). 



128. Second pronator-extensor of the hind iving (fig. 38 B). — Lies 

 close behind I2j; attached dorsally on second basalar plate {2Ba), 

 ventrally on lateral rim of coxa (fig. 38, D, F, 128) anterior to pleural 

 articulation (c). 



I2p. Depressor-extensor of the hind wing (fig. 38 B). — A powerful 

 muscle, attached dorsally on inner disc of subalar plate (Sa), and 

 ventrally on wide hasicostal surface of meral region of coxa (fig. 38 D, 

 F, I2p). 



