NO. 12 



FLYING APPARATUS OF BLOW-FLY — RITTER 



23 



are very well developed, while the direct muscles which serve chiefly 

 for steering are small and weak. 



Kiinckel (1875, p. 175) divides the entire musculature of the 

 Diptera into three groups, the depressors (abaisseurs), the elevators 

 (elevateurs) and the steering muscles (directeurs). The depressors 

 and elevators are indirect, the steering direct muscles. 



A. INDIRECT MUSCLES 



A pair of powerful muscles, the musculi dorsales (Kiinckel, 1875, 

 p. 175) (text fig. 4, mm; pi. 4. fig- 7> '"w; pl- i~' ^S- 3i. ww) trav- 



el v II 



t r 



a p 



m 



Fig. 5. Diagrammatic view of the more laterally lying indirect muscles. 

 (Median section of the thorax.) 



ap, Mesapophysis. 



dvl, Musculus dorsalis-ventralis primus. 

 dvll, Musculus dorsalis-ventralis secundus, 

 dvIII, Musculus dorsalis-ventralis tertius. 



■ m, Musculus latus. 

 st, Stigma anterius. 

 tr, Trochanter muscle. 



erse the entire length of the thorax. Each of these consist of six 

 separate parts of unequal length. The first, dorsal portion, extends 

 from the boundary between the scutellum and postscutellum of the 

 mesothorax to about the middle of the scutum, where it is inserted. 

 Between this muscle, the scutellum and the anal portion of the 

 scutum there is an empty (air-filled) space (pi. 12, fig. 31, lu) which 

 is to be regarded as an air-sac. 



