INSECTS: WINGS AND THEIR APPENDAGES 111 



proach the character of true voices; at least so far as they 

 are produced by the emission of air from the breathing 

 organs. One of the most eminent of Continental entomolo- 

 gists, 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 the last case the sound 

 was somewhat weaker and higher) he conceived that the 

 spiracles 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. Pursuing his researches, 

 he extracted one of these spiracles, and opening it care- 

 fully, found its posterior and inner lip, which is directed 

 toward the commencement of the trachea, to be expanded 

 into a small, flat, crescent- shaped plate, upon which are 

 nine parallel, very delicate, horny laminae, the central one 

 being the largest, while those on each side become grad- 

 ually smaller and lower; so it is, he is persuaded, in con- 

 sequence of the air being forcibly driven out of the trachea 

 and touching these laminae that they are made to vibrate 

 and sound, precisely in the same way with the glottis of 

 the larynx. Dr. Burmeister (who remarks that Chabrier, 

 in his "Essai sur le Yol des Insectes," p. 45, etc., has also 

 explained the hum of insects as produced by the air stream- 

 ing from the thorax during flight, and also speaks of lam- 

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

 be certain that the laminae 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 laminae. He explains the 

 weaker and sharper tones produced when the wings, all 



