MUSCULATURE OF DIPTERA — SMART 357 



compared with the other indirect flight muscles (Smart, 1957). The 

 coxosubalar muscle of Anisopus is small (fig. 4, 10). 



Smart (loc. cit.) has drawn attention to the fact that the CS muscle 

 in Anisopus and Ptychoptera is of the fibrillar type similar to the 

 indirect flight muscles, and not of the tubular type like the direct 

 flight muscles of the pleural musculature. In Panorpa (Mecoptera) 

 the indirect flight muscles, TDT muscle, CS muscle, and other pleural 

 and leg muscles are all of one histological type and do not appear to 

 be separable into fibrillar and tubular types as in Diptera. 



While examining a large number of Diptera for the presence or 

 absence of the TDT muscle (Smart, 1958) I came to the following 

 conclusions about the CS muscle in Diptera : ( i ) Nematocera which 

 lack the TDT muscle possess a CS muscle. (2) At least some of 

 those few Nematocera which possess a TDT muscle possess a CS 

 muscle. (3) No Brachycera (Brachycera-Orthorrhapha auct.) or 

 Cyclorrhapha ( = Brachycera-Cyclorrhapha auct.) possess a CS 

 muscle irrespective of their possession or lack of a TDT muscle. 



Snodgrass (1935) says, "In the mesothorax of the higher Diptera 

 the single subalar muscle arises on the lower part of the epimeron 

 dorsal to the meron, but this muscle is probably the usual subalar- 

 coxal muscle transposed from the displaced meron to the pleural wall." 

 From what has been said above it seems that most students of the 

 muscle anatomy of Diptera do not concur with Snodgrass's view on 

 this matter. This reluctance finds some support from the fact that 

 in Nematocera that possess the CS muscle, it is (Smart, 1957) a 

 fibrillar muscle similar to the indirect flight muscles. I suspect that 

 the muscle Snodgrass had in mind when he made the above observa- 

 tion was that now identified in the mesothorax of Anisopus as an 

 axillary muscle of the 4th sclerite (D, 9, c, ii). 



8. CONCLUDING COMMENTS 



The investigations reported upon in these notes were commenced 

 in the belief, frequently mentioned in literature about Diptera (see 

 Introduction), that Anisopus was a primitive dipteron and that greater 

 knowledge of its anatomy would prove to be a help in elucidating 

 general phylogenetic problems in Diptera. Soon, however, it became 

 apparent that, in respect to the mesothoracic musculature, Anisopus 

 was not primitive. 



In the course of the investigation of the musculature of Anisopus 

 a considerable number of examples of various famihes of Diptera 

 were dissected and the relevant literature was examined. Some inter- 



