280 



HITCHCOCK'S ANATOMY 



tune is greatly increased by the construction of the trachea 

 and bronchi. " Birds whose voices have a very extensive 

 musical scale are able to shorten and lengthen their wind- 

 pipe considerably, and to that end have very thin wings and 

 large membranous interspaces." 



495. Larynx of Reptiles. — Reptiles have an imperfect 

 kind of larnyx, which is located at the point where the trachea 

 opens into the pharynx. The only sounds w^hich they can 

 make is the croak of the frog and hiss of the serpent, turtle, 

 or lizard. The common Frog has two vesicles or little bags 

 behind the angle of the mouth, which are much distended at 

 the beginning of summer and at pairing time, which accounts 

 for their loud croaking at these seasons. 



496. Sounds Made by Insects, — As we descend the scale 

 of animals, we find in no other a larynx or organ of voice, 

 and hence all the sounds made by them are not the sounds 

 of the voice, but simply noises which are for the most part 

 made by their extremities. The sounds made by insects such 

 as approach most nearly to those of vertebrate animals, are 

 produced by vibrations of a membranous plate situated just 

 over the spiracles. And in general those insects that fly the 

 most rapidly, and whose wings move the fastest, make the 

 most noise, while those which move more slowly seem only to 

 fan the air with their wings. Other sounds are produced by 

 mastication. Thus, an army of locusts, when eating, makes a 

 sound which very much resembles the noise of a crackling fire. 

 A genus of ants make a sound by striking some hard sub- 

 stance with their mandibles, or arm-like appendages. A 

 species of beetle that bores in old timber (called the death 

 watch) makes a sound in a similar way, and if it be answered 

 by its mate the signal will be repeated : but if no answer be 

 given, the animal changes its position before it produces its 

 " tick" again. The shrill sound of the grasshopper and the 



What ase is it? What construction increases the intensity of their tones? 495. What 

 is the larynx of reptiles? WTiat is their voice? 496. Do insects have a larynx? In 

 what different ways are sounds made by insects ? 



