306 



NOISES OF INSECTS. 



To be convinced of this, he affirms, the observer has nothing 

 to do but to hold each wing with the finger and thumb, and 

 stretching them out, taking care not to hurt the animal, in 

 opposite directions, thus to prevent their motion, — and im- 

 mediately all sound will cease. For further satisfaction he 

 made the following experiment. He first cut off the wings 

 of one of these flies very near the base ; but finding that it 

 still continued to buzz as before, he thought that the winglets 

 and poisers, which he remarked were in a constant vibration, 

 might occasion the sound. Upon this, cutting both off, he 

 examined the mutilated fly with a microscope, and found 

 that the remaining fragments of the wings were in constant 

 motion all the time that the buzzing continued; but that 

 upon pulling them up by the roots all sound ceased. 1 

 Shelver's experiments, noticed in my last letter, go to prove, 

 with respect to the insects that he examined, that the wing- 

 lets are more particularly concerned with the buzzing. 

 Upon cutting off the wings of a fly — but he does not state 

 that he pulled them up by the roots — he found the sound 

 continued. He next cut off the poisers — the buzzing went 

 on. This experiment was repeated eighteen times with the 

 same result. Lastly, when he took off the winglets, either 

 wholly or partially, the buzzing ceased. This, however, if 

 correct, can only be a cause of this noise in the insects that 

 have winglets. Numbers have them not. He next, there- 

 fore, cut off the poisers of a crane-fly ( Tipula crocata), and 

 found that it buzzed when it moved the wing. He cut off 

 half the latter, yet still the sound continued ; but when he 

 had cut off the whole of these organs the sound entirely 

 ceased. 2 



Dr. Burmeister, however, was led by his experiments to a 

 different conclusion. Finding that the buzz of a large fly 

 (Eristalis tenax) still continued after the winglets, the 

 poisers, and even the wings had been quite cut off except 

 their very stumps (only in this last case the sound was 

 somewhat weaker and higher), he conceived that the spiracles 

 lying between the meso- and meta-thorax must be the instru- 



1 De Geer. vi. 13. 2 Wiedemann's Archiv. ii. 210. 217. 



