94 EVENINGS AT THE MICKOSCOPE. 



there appears to be some positive colour in their sub- 

 stance ; for in these latter scales, which projecting be- 

 yond the edge of the wing-case can be examined as trans- 

 parent objects, and that with a high power, the trans- 

 mitted light is richly coloured with the same tints as 

 the same scales displayed under the Lieberkuhn. 



We may derive pleasant instruction from contiauing 

 our observations on a few other wings of insects. If 

 you have ever thought on the subject, you have pro- 

 bably taken for granted that the various sounds pro- 

 duced by insects are voices uttered by their mouths. 

 But it is not so. No insect has anything approaching 

 to a voice. Vocal sounds are produced by the emission 

 of air from the lungs variously modified by the organs 

 of the mouth. But no insect breathes through its 

 mouth ; no air is expelled thence in a single species ; it 

 is a biting, or piercing, or sucking organ ; an organ for 

 the taking of food, or an organ for offence or defence ; 

 but never an organ of sound. 



The wings are in most cases the immediate causes 

 of insect sounds. On this subject you will read with 

 pleasure some very interesting remarks by the learned 

 Mr. Kirby, inquiring, " by what means these sounds 

 are produced." 



" Ordinarily, except perhaps in the case of the gnat, 

 they seem perfectly independent of the will of the ani- 

 mal ; and, in almost every instance, the sole instruments 

 that cause the noise of flying insects are their wings, or 

 some parts near to them, which, by their friction 

 agaiast the trunk, occasion a vibration — as the fingers 

 upon the strings of a guitar — yielding a sound more or 

 less acute in proportion to the rapidity of their fiight, 

 the action of the air perhaps upon these organs giving 



