MACHINERY OF INSECT FLIGHT 



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Fig. 1. A. Left side of thorax of Sarcophaga bullata. B. Ventral view of scutellar 

 lever dissected free from the thorax. C. Detail of lever arm and attachment to scutel- 

 lum, outside above and inside view below : a, scutellum ; b, lever arm ; c, process 

 articulating with the first axillary sclerite ; d, anterior parascutum ; e, posterior 

 parascutum ; f, junction of prescutal ridge, transverse ridge and parascutal hinge; 

 g, end of parascutal hinge ; h, point in line of attachment of notum with lever arm ; 

 i, point of rotation of the scutellar lever on the postnotum ; j-k, fulcrum of the notum 

 lever in the action of vertical muscles ; 1-m, line of attachment of notum with lever 

 arm ; n-o, lateral vertical cleft ; p, anterior notal process ; q, transverse ridge ; r, arti- 

 culating groove for attachment of postnotum ; s, scutellar bridge ; t, triangular struc- 

 ture supporting articulation of lever and postnotum ; u, groove for a process of first 

 axillary sclerite. 



thus rotating the scutellum downward. The forward-projecting arms b of 

 the scutellum act upon the wing articulation to force the wings down. The 

 shortening of the vertical muscles ( 1, 2, 3, Fig. 2) pulls the tergum down 

 and forward, forcing joint i of the scutellum posteriorly. By this action 

 the longitudinal muscles are restretched, the scutellum is rotated upward, 

 and the arms of the scutellum move down, thereby forcing the wings up. 



