NOISE OF INSECTS. 371 



be considered as a kind of love-song, when it is in a 

 state of nature and free ; but it emits a cry of the same 

 kind when captured, upon occasions when fear must be 

 the prevailing passion. 



The noise which this, or indeed any other insect, 

 emits, is not a cry or voice of any kind, as those terms 

 are understood among mankind, that is, produced by 

 the action of certain organs upon the breath, emitted by 

 the animal in respiration, for insects have no such organi- 

 zation. The sounds which they produce arise from the 

 action of some part upon the external air, and are effected 

 generally by the rapid vibration of such part of their 

 bodies or their wings, or the rubbing or striking of 

 one part against another. The sound of the common 

 death-watch, which has been so often and so foolishly 

 considered as counting up the moments of human life, 

 is practised by the insect drumming upon wood with 

 its hard and stiff mandibles, in order that its mate may 

 answer to its call. Sometimes the sounds are produced 

 by grating against each other the horny edges of the 

 elytra or wing-covers ; in a few instances the insect is 

 provided with a natural drum, or elastic plate drawn 

 over some hollow, by which a vibrating motion is given 

 to the air, and sound produced ; and in the case of the 

 death's-head moth, Reaumur found out that the noise 

 which it makes when confined, proceeds from the friction 

 of the palpi against the mandible, which, though a sound 

 originating in part in the mouth, yet can, in no sense 

 of the word, be considered as voice. Voice, or not 

 voice, this sound is obviously intended to answer only 

 insect purposes, though how it affects them has not been 

 clearly ascertained ; because, with the exception of the 



