ENTOMOLOGY 



against a dark background. Under these conditions, the trajectory 

 of the wing appears as a luminous elongate figure 8. During flight, 

 the trajectory consists of a continuous series of these figures, as in Fig. 



75- 



Marey, an authority on animal locomotion, used chronophotography, 



among other methods, in studying the proc- 

 ess of flight, and obtained at first twenty, 

 and later one hundred and ten, successive 

 photographs per second of a bee in flight. 

 As the wings were vibrating 190 times per 

 second, however, the images evidently 

 FIG. vs.-Tra^ctory^of the wing rep resented isolated and not consecutive 



phases of wing movement. Nevertheless, 



the images could be interpreted without difficulty, in the light of 

 the results obtained by other methods. At length he obtained sharp 

 but isolated images of vibrating wings with an exposure of only ^5,000 

 of a second. 



The frequency of wing vibration may be ascertained from the note 

 made by the wing if it vibrates rapidly enough to make one; and, in 



PIG. 76. Records of wing vibration. A, mosquito, Anopheles. Above is the wing 

 record and below is the record of a tuning-fork which vibrated 264.6 times per second. B, 

 wasp, Polistes. The tuning-fork in this instance had a vibration frequency of 97.6. 



.any case, may be determined graphically by means of a kymograph, 

 which, in one of its forms, consists of a cylinder covered with smoked 

 paper and revolved by clockwork at a uniform rate. The insect is 

 held in such a position that each stroke of the wing makes a record on 

 the smoked paper, as in Fig. 76, A. Comparing this record with one 

 made on the same paper by a tuning-fork of known vibration period, 

 the frequency of wing vibration can be determined with great accuracy. 



