INSECTS: WINGS AND THEIR APPENDAGES 103 



wings, though very rapid, is easily seen; but when they 

 fly off it is no longer visible. Kepeated experiments have 

 been tried to ascertain the cause of sound in this tribe, 

 but it should seem with different results. De Geer, whose 

 observations were made upon one of the flies just men- 

 tioned, appears to have proved that, in the insect he ex- 

 amined, the sounds were produced by the friction of the 

 root or base of the wings against the sides of the cavity 

 in which they are inserted. 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 immediately 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 pois- 

 ers, which he remarked were in a constant vibration, might 

 occasion the sound. Upon this, cutting both off, he exam- 

 ined the mutilated fly with a microscope, and found that 

 the remaining fragments of the wings were in constant mo- 

 tion all the time that the buzzing continued; but that by 

 pulling them up by the roots all sound ceased. Shelver's 

 experiments go to prove, with respect to the insects that 

 he examined, that the winglets are more particularly con- 

 cerned 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 re- 

 peated 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 



