CHAPTER XVIII. 

 ORDERS OF INSECTS. 



THE known number of insects is so enormous, their forms 

 are so various, and their habits and instincts are not only so 

 remarkable but have been so fully described, that it were 

 hopeless to attempt here to do more than give the briefest 

 possible outline of the leading characters which distinguish 

 the different orders. The student desirous of further informa- 

 tion on this head must have recourse to treatises specially de- 

 voted to entomology. 



SECTION I. AMETABOLIC INSECTS. Young not passing 

 through a metamorphosis , and differing from the adult in 

 size only. Perfect insect (imago) destitute of wings; eyes 

 simple, sometimes wanting. 



ORDER I. ANOPLURA (Gr. anoplos, unarmed ; our a, tail). 

 The insects comprised in this order are parasitic upon man 

 and other animals, and they are commonly known as Lice. 

 They are all very minute in size, destitute of wings in the 

 adult state, having a mouth formed for suction, and having 

 either two simple eyes or none. 



ORDER II. MALLOPHAGA (Gr. m,allos, a fleece ; phago, I 

 eat). These are known as "Bird-lice," and are all minute 

 parasites on different birds. They are distinguished from the 

 true lice by not living upon the juices of their host, but upon 

 the more delicate and tender appendages of the skin. The 

 mouth is, consequently, not suctorial, but fitted for biting. 



ORDER III. THTSANURA (Gr. thusanoi, fringe ; oura, tail). 

 The most familiar members of this order are the " Spring- 



