MANUAL OF NATUEAL HISTORY. 265 



enabled to leap and spring about. They feed on de- 

 caying animal and vegetable matter. The Sugar- 

 lice, constituting the other section, are little active 

 animals, covered with bright silvery scales. They 

 are often seen running briskly about among old 

 books and boards. They have simple eyes, like 

 those of spiders, on each side of the head ; and, in 

 some respects, resemble Myriapods. Their antennae 

 are setaceous and elongated, and there are three 

 setaceous appendages at the end of the tail. 



The young Parasites differ from the parent only 

 in size. Nearly every kind of quadruped and bird 

 harbours species of these animals ; and even in the 

 human subject they have been known, by an exces- 

 sive multiplication, perhaps induced by want of 

 cleanliness, to have produced a loathsome disease, 

 from which it is said Herod, Sylla, Antiochus, and 

 Calisthenes perished. These pestiferous insects, in- 

 cluding the Louse and its allies, have six feet formed 

 for walking ; their mouth is furnished with a sucto- 

 rial proboscis; their antennae are as long as the 

 thorax; their abdomen is depressed and formed of 

 several segments ; and their mode of respiration is 

 by tracheal tubes as in the insect races. 



II. CLASS. AIOLOPODS (Aiolopoda). 



Animal breathing through stomata by means of 

 respiratory tubes or tracheae ; apterous ; head dis- 

 tinct, with two antennae. Undergoing no regular 

 metamorphosis, but casting their skin like Crusta- 

 ceans. 



