334 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I37 



In the mesopleural wall there is no difficulty in tracing the pleural 

 sulcus from the true articulation of the coxa to the wing root. In 

 front of the sulcus can be distinguished, using the dipterists' descrip- 

 tive terminology, an episternal area above and the large sternopleural 

 area below. Whether these two areas are in fact an anepisternum and 

 a katepisternum seems still a matter for debate; Snodgrass (1935) 



Fig. I. — Anisopus fcnestralis Scop., lateral external view of thorax. X 42. 



designated the former the episternal area and the latter he called the 

 precoxal area ; the sternopleural areas meet in the midline anterior to 

 the invaginated cryptosternum, and the fact that the more anterior 

 dorsoventral indirect flight muscles are inserted on them suggests 

 that they may be composite structures and comprise both episternal 

 and coxal elements which are now indistinguishable. Posterior to the 

 pleural sulcus an anepimeron and a katepimeron can be distinguished. 



