ON- INSECT SOUNDS. 229 



the real basis of voice. If the mouth be fully opened, and the 

 cavities of fauces and mouth be fixed, the initial reed tone is 

 greatly intensified by adding sonorous open tones or harmonics 

 of the primary tone. The vowel sounds thus produced are 

 compound tones, whose characteristic quality depends on the 

 particular shape and position in which the mouth, jaw. and fauces 

 are for the time retained. If the fall reed tone be produced, 

 and, together with the additional tones obtained from vibration 

 produced above the larynx, be articulated by suitable movements, 

 complete vocalization, comprising variously combined vowels and 

 consonants, is the result. Each vowel sound has its ground note 

 and harmonics, and if sounded with great power the added 

 harmonies prevail so as to render the ground tone more sonorous ; 

 but in whispered speech the vowels are principally made up of the 

 ground tone produced in the cavity of the mouth, through which 

 air is gently breathed. Consonants are only noises formed by 

 movements of the palate, lips, &:c. Thus noise and tone are 

 associated in the human voice. 



Now in many insects — and notably bees, flies, gnats, and the 

 wonderful singing cicada — the analogue of this human vocal organ 

 is to be found in the breathing spiracles of its chest, two pairs of 

 which are transformed into vocal organs : the tone produced is a 

 reed sound, and the vocal membrane is in some insects furnished 

 with muscles, and stretched upon an elastic ring, which arrange- 

 ment enables the pitch to be varied. The insect has, in short, a 

 singing voice, and instead of wanting a mouth, it has one or two 

 pairs of mouths, whilst the vocal apparatus is enclosed in a 

 considerable cavity which is resonant. In fact the insect in 

 proportion to its size and weight has a vocal organ, the 

 dimensions and power of which are on a scale immeasureably 

 greater than in man. 



It is, however, not a necessary inference that the insect apparatus 

 is directed by any volition, though the insect seems to exercise its 

 voice at will. Certain states of bodily sensation, may bv reflex 



