MACHINERY OF INSECT FLIGHT 



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wing is tied in with the anterior notal process and the 1st axillary e. The 

 wing cycle reflects primarily the movement of this point of union. On the 

 down stroke, k is moved up by the action of the scutellar lever on the 1st 

 axillary sclerite, and moved posteriorly, due to the movement of the tergum 

 transmitted through the anterior notal process and the parascutum. As a re- 

 sult the wings move down and forward with proper changes in tilt. On the 

 return stroke the reverse action of the parts brings the wings back to the up 

 position. The union point k moves in a cycle as it follows different paths 

 on the up and down strokes. 



A 



B 



Fig. 3. Cross-sectional view of thorax showing details of the articulation of the 

 right wing. A. Wing in up position, anterior view. B. Wing in the down position, 

 anterior view. C. Posterior view of the axillary sclerites of right wing showing their 

 relation to the mesopleural process, the lever arm, and the anterior parascutum : a, 

 mesopleural process ; b, pleural apophysis ; c, anterior pleurosternal muscle ; d, an- 

 terior parascutum ; e, first axillary sclerite ; f, second axillary sclerite ; g, base of 

 radial vein; h, hinge; i, radial vein; j, hook articulation; k, point of articulation of 

 anterior notal process, first axillary sclerite, base of radial vein, and second axillary 

 sclerite ; 1, end of the lever arm. 



When the articulation is set for flight or by the action of CCI4, the hinge 

 of the parascutum and the mesopleural process are brought closer together. 

 This results from an outward thrust at / (Fig. 1), the junction of the pre- 

 scutal and transverse ridges, produced by tension in the indirect muscles, 



