MUSCULATURE OF DIPTERA — SMART 347 



10. COXOSUBALAR MUSCLE (fIG. 4), 



Other names are: Coxosubalar epipleural muscle "3E" (Snod- 

 grass), coxosubalar muscle (Maki), coxosubalar muscle (Bonhag, 

 but absent in Tabanus which he actually described). 



This is a specialized muscle as has been pointed out by Smart 

 (1957). It is of the fibrillar type like the large indirect flight muscles 

 of the mesothorax and comprises two giant fibers. Its function has 

 been discussed by Pringle (1957). It originates on the meron of the 

 mesothorax and inserts on the subalar plate. It is not present in 

 Calliphora or Drosophila and so was not named by Ritter or by Miller 

 in Demerec respectively. The coxosubalar muscle is mentioned im- 

 mediately above and discussed elsewhere in this paper. 



11. PLEUROSTERNAL MUSCLES (PL. I, FIG. fl). 



The cryptosternum of Anisopus has a distinctive well-developed 

 furca. The furca has a heavily sclerotized stalk which divides into 

 two arms. The arms are expanded into a large dorsal cup facing 

 upward toward the pleural sulcus and a smaller cup opposite the 

 pleural sulcus at a point just above the articulation of the coxa. The 

 pleurosternal muscles are in fact muscles that link the pleural wall at 

 the sulcus to the cups of the furca. Their function must be largely 

 to hold the pleural wall firmly in position when the insect is flying. 



From the underside of the furcal cups there originates the broad- 

 based furcotrochanteral depressors of the trochanter (E, 12). 



a. Superior pleurosternal muscle. 



Other names are: Pleurosternal muscle (Snodgrass), musculus 

 latus (Ritter), furcoentopleural muscle (Maki), anterior pleurosternal 

 muscle (Bonhag), pleurosternal muscle (Miller in Demerec). 



This powerful muscle is broadly based on the upper cup of the 

 furca and narrows down to insert along the pleural sulcus. It must 

 have considerable strength, but its shape would indicate that its power- 

 ful contraction probably acts only through a very short distance. This 

 suggests that its function is to maintain the position of the pleural 

 wall in relation to the furca rather than to cause any modification in 

 relative positions. 



h. Inferior pleurosternal muscle. 



Other names are: Pleurosternal muscle (Snodgrass), furcoento- 

 pleural muscle (Maki), posterior pleurosternal muscle (Bonhag), 

 pleurosternal muscle (Miller in Demerec). 



