NOISES OF INSECTS. 523 



and lower ; and it is, he is persuaded, in consequence 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 Vol dcs Insectes, p. 45, &tc., has also explained the hum of insects 

 as produced by the air streaming from the thorax during flight, and also 

 speaks of laminae which lie at the aperture of the spiracle), 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 ante- 

 rior ones, but without finding in them any trace of these laminae. He 

 explains the weaker and sharper tones produced when the wings all but 

 the very roots are cut off as resulting from the weaker vibrations of the 

 contracting muscles, and consequent less forcible expulsion of the air 

 when the vibratory organs are removed ; and he thinks with Chabrier that 

 some air may escape through the open trachea of the wings which are 

 cut off. Though he regards these laminae as the cause of humming In 

 bees and flies, he does not decide that other causes may not produce the 

 buzz of cock-chafers, &,c., in the thoracic spiracles of which he could not 

 discern them.^ 



Aristoplianes, in his Clouds, deriding Socrates, introduces Chaerephon 

 as asking that philosopher whether gnats made their buzz with their 

 mouth or their tail.^ Upon which MoufFet very gravely observes, 

 that the sound of one of these insects approaching is much more acute 

 than that of one retiring; from whence he very sapiently concludes, that 

 not the tail but the mouth must be their organ of sound.^ But after all, 

 the friction of the base of the wings against the thorax seems to be the 

 sole cause of the alarming buzz of the gnat as well as that of other Dip- 

 tera. The warmer the weather, the greater is their thirst for blood, the 

 more forcible their flight, the motion of their wings more rapid, and the 

 sound produced by that motion more intense. In the night — but perhaps 

 this may arise from the universal stillness that then reigns — their hum 

 appears louder than in the day: whence its tones may seem to be modi- 

 fied by the will of the animal. 



Sounds, also, are sometimes emitted by insects when they are feeding or 

 otherwise employed. The action of the jaws of a large number of cock- 

 chafers produces a noise resembling the sawing of timber ; that of the locusts 

 has been compared to the crackling of a flame of fire driven by the wind ; 

 indeed the collision at the same instant of myriads of millions of their 

 powerful jaws must be attended by a considerable sound. The timber- 

 borers also — the Buprestes ; the stag-horn beetles ; and particularly the 

 capricorn-beetles — the mandibles of whose larvae resemble a pair of mill- 

 stones'* — most probably do not feed in silence. A little wood-louse 

 (Atropos pulsatoria) — which on that account has been confounded with 

 the death-watch — is said also, when so engaged, to emit a ticking noise. 

 Certain two-winged flies seen in spring, distinguished by a very long 

 proboscis (^Bombylius), hum all the time that they suck the honey from 

 the flowers ; as do also many hawk-moths, particularly that called from 



> Burmeisier, Manual of Ent. 408—470. » Act i. Sc. 2. 



3 Mouffet, 81. « Linn. Trans, v. 225. t. xii. f. 7. b. 



