insects: wings and their appendages. 91 



In some instances the sounds of insects more nearly 

 approach the character of true voices ; at least so far as 

 they are produced by the emission of air from the breath- 

 ing organs, yet not by means of the mouth. One of the 

 most eminent of living entomologists, Dr. Burmeister, 

 tells us so. Finding that the buzz of a large fly (Eristalis 

 tenax) still continued after the winglets, the poisers, and 

 even the wings, had been quite cut off except their stumps 

 (only in this last case the sound was somewhat weaker 

 and higher), he conceived that the spiracles, or breathing 

 holes, lying between the meso- and meta-thorax must be 

 the instruments of the sound; which, accordingly, he 

 found to cease entirely when they were stopped with 

 gum, though while the wings were in vibration. Pur- 

 suing his researches, he extracted one of these spiracles, 

 and opening it carefully, found its posterior and inner 

 lip, which is directed towards the commencement of the 

 trachea, to be expanded into a small, flat, crescent-shaped 

 plate, upon which are nine parallel, very delicate, horny 

 lamina 3 , the central one being the largest, while those on 

 each side become gradually smaller and lower; so it is, 

 he is persuaded, in consequence of the air being forcibly 

 driven out of the trachea and touching these lamince, 

 that they are made to vibrate and sound, precisely in 

 the same way as with the glottis of the larynx. Dr. 

 Burmeister (who remarks that Chabrier, in his Essai sur 

 le Vol cles Insectes, p. 45, etc., has also explained the 

 hum of insects as produced by the air streaming from 

 the thorax during flight, and also speaks of lamina;, 

 which lie at the aperture of the spiracles), in order to 

 be certain that the lamina? in question in the posterior 

 spiracles of the thorax are alone concerned in producing 

 sound, also inspected the anterior ones, but without find- 

 ing in them any trace of these lamime. He explains 

 the weaker and sharper tones produced when the wings, 

 all but the very roots, are cut off, as resulting from the 



