MUSCULATURE OF DIPTERA — SMART 34I 



5. TERGOMERAL (INDIRECT FLIGHT) MUSCLE (fIG. 3). 



Other names are: Tergal remoter of leg (Snodgrass), 2d dorso- 

 ventral muscle (Ritter), tergal remotor of coxa (Maki), 2d dorso- 

 ventral muscle (Bonhag), tergal remotor of coxa (Miller in 

 Demerec). 



This large muscle consists of two or three giant fibers. It lies pos- 

 terior to the muscles running from the pleural wall to the furca 

 (D, 11) and runs from the scutum to the "hypopleuron" or meron 

 of the mesocoxa. In Anisopus the meron, while distinct from the 

 coxa vera, is not completely fused to the pleural wall of the meso- 

 thorax and has very little freedom of movement. The muscle acts 

 as an indirect elevator of the wing. 



(6). TERGAL DEPRESSOR OF TROCHANTER. 



Other names are: Tergal branch of extracoxal depressor of tro- 

 chanter (Snodgrass), trochanter muscle (Ritter), tergal depressor of 

 trochanter (Maki), (tergal) branch of depressor of trochanter (Bon- 

 hag), extracoxal depressor of trochanter (Miller in Demerec). 



This muscle is not found in Anisopus, nor is there any muscle that 

 can be regarded as homologous with it. A general discussion of this 

 muscle as it occurs among Diptera will be found elsewhere in this 

 paper. It is, when present, a muscle of the usual tubular, tetanic type, 

 not of the giant-fiber type like the indirect flight muscles discussed 

 above. 



Snodgrass (1935) in the course of his discussion of the generalized 

 musculature of the winged thoracic segment has commented on the 

 condition in the mesothorax of Diptera. 



In the generalized winged thoracic segment the following major 

 dorsoventral muscles would be sought for : i, A tergosternal muscle 

 (Snodgrass's term) ; ii, a tergal promoter of the leg (Snodgrass's 

 term) inserting on the trochantin ; iii, a tergal remotor of leg (Snod- 

 grass's term) inserting on the posterior rim of the coxa, i.e., the 

 meron ; iv, a tergal branch of the extracoxal depressor of the tro- 

 chanter (Snodgrass's term). 



In Diptera, in addition to the obhque dorsal muscle, there appear 

 to be only two large dorsoventral indirect flight muscles. The tergal 

 branch of the extracoxal depressor of the trochanter (C, 6) may be 

 present or absent ; it is always readily identified when present, or its 

 absence is obvious. 



