354 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 37 



been considered in the literature in this respect there are not more 

 than two coxal depressor muscles of the trochanter and these insert 

 on the mesial depressor tendon along with the furcal depressor and 

 with the tergal depressor when it is present. 



Miller in Demerec (1950) pointed out that the TDT muscle in 

 Drosophila was a "tubular" muscle similar to the muscles of the 

 pleural wall and not of the fibrillar type like the indirect flight muscles, 

 though it resembled the latter rather than the former in size. This 

 condition holds in other Diptera that possess the TDT muscle. 



The "fibrillar" type of indirect flight muscle is characteristic of the 

 Hymenoptera and Diptera (Snodgrass, 1925), and it is therefore not 



Table 4. — Tergal depressor of trochanter muscle in Diptera 

 (Derived from Smart, 1958) 



1. Nematocera having TDT muscle: Simuliids, sciarids, psychodids, Nemopal- 



pus. 



2. Nematocera lacking TDT muscle: Trichocera, Anisopiis, Mycetobia, tipulids, 



Ptychoptcra, Thaiimalea, culicids, mycetophilids, chironomids, cecidomyiids, 

 blepharocerids, bibionids, scatopsids. 



3. Brachycera having TDT muscle: Some stratiomyiids, Tabanus, Haernato- 



pota, Chrysops, Pclecorhynchus, Scaptia, rhagionids, therevids, scenopinids, 

 some bombyliids, empids, dolichopodids. 



4. Brachycera lacking TDT muscle : Some stratiomyiids, Pangonia, Coenotnyia, 



some bombyliids, asilids, acrocerids. 



5. Cyclorrhapha having TDT muscle : Lonchopterids, phorids, conopids, all 



acalypterates examined, Calliphora, Sarcophaga, Rutilia, tachinids. Oestrus, 

 Hypoderma, Cuterebra, Scatophaga, muscids, Stomoxys. 



6. Cyclorrhapha lacking TDT muscle : Pipunculids, Gastcrophilus, Glossina, 



Hippobosca. 



surprising that no such difference between the TDT muscle and the 

 indirect flight muscles has been reported by those working on the 

 musculature of such insects as the cockroach (Carbonnell, 1947) or 

 the grasshopper or locust (Snodgrass, 1935, etc.; Albrecht, 1953). 



There is a TDT muscle in the prothorax and the metathorax of the 

 cockroach (Carbonnell, 1947). Maki (1938) states that he found a 

 TDT muscle in all three segments of Lepisma; perhaps the TDT 

 muscle is basic to the general musculature of the hexapod thoracic 

 leg segment regardless of the presence or absence of a wing. 



Maki (1938) reported that in the tipulid, Ctenacroscelis, there was 

 no mesothoracic TDT muscle (see pi. i, fig. c), that one was present 

 in the metathorax, and that there was a "pleural depressor of the 

 trochanter" in the prothorax. 



In Anisopus, which has no TDT muscle in the mesothorax, there 



