SOUNDS PRODUCED IN FLIGHT. 71 



Indeed, from the note produced we can calculate the 

 rapidity of the vibration. The slow flapping of a 

 butterfly's wing- produces no sound, but when the move- 

 ments are rapid a noise is produced, which increases 

 in shrillness with the number of vibrations. Thus the 

 house-fly, which produces the sound of F, vibrates its 

 wings 21,120 times in a minute, or 335 times in a 

 second ; and the bee, which makes a sound of A', as 

 many as 26,400 times, or 440 times in a second. On 

 the contrary, a tired bee hums on E', and therefore, 

 according to theory, vibrates its wings only 330 times 

 in a second. 



Marey has succeeded in confirming these numbers 

 graphically. He fixed a fly so that the tip of the 

 wing just touched a cylinder which was moved by 

 clockwork. Each stroke of the wing caused a mark, 

 of course very slight, but still quite perceptible, and 

 he thus showed that there were actually 330 strokes in 

 a second, agreeing almost exactly with the number 

 inferred from the note produced. 



The sound emitted from the spiracles bears no re- 

 lation to that produced by the wings. Thus, according 

 to Landois, the wing-tone of the hive bee is A'; its 

 " voice," if we may call it so, on the contrary, is an 

 octave higher, and often goes to B" and C". In one of 

 the solitary bees, Anthidium manicatum, the difference 

 is still greater ; the wing-tone is G', and the " voice " 

 nearly two octaves higher, reaching to F'". 



The wing-tone is constant, at least with the excep- 

 tions just alluded to. The " voice," on the contrary, 

 appears to be to some extent under the control of the 

 will, and thus offers another point of similarity to a true 

 " voice." Thus a bee in the pursuit of honey hums 



