MACHINERY OF INSECT FLIGHT 



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posterior rotations evident in the anterior notal process record, where for 

 part of the cycle the light is moving forward faster than the film. 



Fig. 4. Movements of the thoracic structures. A, fly, Sarcophaga ; B, wasp, Po- 

 listes ; C, fly, Sarcophaga. Records of optical levers from mirrors attached to the 

 scutellum (and moving with the scutellar levers ScL), to the mesopleural process 

 (MP), and to the tergum just above the parascutum where in-and-out movements of 

 the anterior notal process (ANP) are effective. In A and C the original records are 

 traced and movements are tilting the mirrors not only in the vertical axis but to 

 various degrees horizontally, with or against the time axis. In B the record has been 

 redrawn to eliminate anterior-posterior movements and the three beams shifted so 

 that simultaneous movements of time are vertically under each other. In A and C 

 the time correspondence is indicated by the dotted segments. The terms up and down 

 refer to wing position ; in and out to lateral movement of the part relative to the 

 thorax. 



From the static analysis (Fig. 3) based on CCl^-treated flies, it was 

 predicted that, at the beginning of a stroke, the anterior notal process moves 

 in (light beam down) while the mesopleural process moves out (light beam 

 down). After the critical period, the mesopleural process moves in (light 

 beam up) and the anterior notal process out (light beam up). The record 



