94 EYENENGS AT THE IVnCEOSCOPE. 



there ap2)eai's 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 continuing 

 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. Yocal 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 ail organ for ofl'ence or defence ; 

 but never an organ of sound. 



The wino;s 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 

 Bomc parts near to them, which, by their friction 

 against the trunk, occasion a vibration — as the fingers 

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

 less acute in proportion to the rapidity of their flight, 

 the action of the air perhaps upon these organs giving 



