NO. I 



INSECT THORAX — SNODGRASS 



65 



the basisternum anterior to the coxa, but other muscles are often 

 accessory to these. As just noted, the obHque dorsals may be wing 

 elevators. In the mesothorax of Diptera the remotor of the coxa, 

 which arises dorsally on the scutum and is attached ventrally on the 

 meron of the coxa, becomes a wing elevator through the transfer of 

 the meron from the coxa to the wall of the segment (fig. 34 D, /), 



The epipleural (basalar and subalar) coxal muscles, and the mus- 

 cles of the third axillary constitute the direct zviug muscles, so called 

 because they act more immediately on the wing, though the epipleural 



B PN 



,^Pph 



1 / 



Bs SA Fs 



Fig. 28. — Diagram of the principal muscles of a wing-bearing thoracic seg- 

 ment, exclusive of the leg muscles, right side, internal view. 



A, dorsal longitudinal muscle attached to successive phragmata, indirect wing 

 depressor ; B, oblique dorsal muscle from scutum to posterior phragma ; C, tergo- 

 sternal muscle from scutum to basisternum, indirect wing elevator ; D, wing 

 flexor of third axillary sclerite; E, basalar muscle of coxa, direct extensor of 

 wing; F, subalar muscle of coxa, direct extensor and depressor of wing; 

 G. pleuro-sternal muscle from pleural apophysis to sternal apophysis ; H, longi- 

 tudinal ventral muscles attached to sternal apophyses. 



muscles are not inserted directly on the wing base, and, as we have 

 seen, are primarily muscles of the leg. The basalar muscle (figs. 28, 

 30 A, E) arises ventrally on the lateral rim of the coxa (Cx) anterior 

 to the pleural articulation; an anterior branch (fig. 30A, E') may 

 arise on the basisternum, on the jirecoxal bridge, or on the epister- 

 num. Since the basalar plate (fig. 30 A, Ba) or the corresponding 

 basalar lobe of the episternum is connected with the anterior angle 

 of the wing base by a ligament-like thickening of the uniting cuticula 

 (a), its muscles have a direct functional relation with the anterior 

 part of the wing base. The subalar muscle (figs. 28, 30 A, F) arises, 

 in typical cases, from the coxal margin posterior to the pleural articu- 



