( 212 ) 



CHAPTER V. 



INSECTS. 



§ 1. Apt era. 



Apterous, or wingless insects form the next term in the 

 series of articulated animals. Closely allied in their organi- 

 zation to many of the preceding families, they differ from 

 them in being essentially formed for a terrestrial instead of 

 an aquatic life. Most of the lower tribes of this order are 

 parasitic, that is derive their nourishment from the juices 

 of other animals, the skin of which they infest and penetrate, 

 and into which they insert tubes for suction. The various 

 tribes oi JJcari, or mites, of Pediculi, or lice, oi Ricini, or 

 ticks, of Pulices^ or fleas: together with the Podura, or 

 spring-tail; the Lepisma, and the family of Myriopoda, or 

 millepedes, are comprehended in this order. I shall be 

 obliged to pass over these tribes very cursorily, noticing 

 only a few of the more remarkable circumstances attending 

 their mechanical conformation. 



The Pulex is the only apterous insect that undergoes com- 

 plete metaphorphoses in the course of its development. In 

 the first stage of its existence, it has the form of a long 

 worm, without feet, frequently rolling itself into a spiral 

 coil. It consists of thirteen segments, having tufts of hair 

 growing upon each. In its mature state, it has six articu- 

 lated legs, the hindmost of which are of great size, for the 

 purpose of enabling the insect to take those prodigious leaps 

 which astonish us in beings of so diminutive a size, and af- 

 ford a striking proof of the exquisite mechanism j^ervading 

 even the lowest orders of the animal creation. 



The Podiira leaps into the air by a mechanical contri- 

 vance of another kind; employing for this purpose the tail, 

 which is very long, and forked at the end. In its ordinary 



