1 6 Descriptive Zoology. 



the mode of life of the other. Let us suppose that they 

 trade places. It is not unfair to make this supposition, for 

 they are not extremely unlike. Both have strong biting 

 jaws, two pairs of strong wings, and a long abdomen. 



In the first place, let us suppose that the dragon fly can 

 subsist on vegetable food, and that it takes up its life as 

 a grasshopper. It finds its long, projecting wings in the 

 way. They not only hinder it as it attempts to crawl 

 into narrow places, but are apt to be torn, for, though 

 strong, their texture is delicate. So it will naturally turn 

 the wings back alongside of the body, and for compact- 

 ness will probably let one pair rest upon the other. It 

 will further protect them if the outer wings become harder 

 and tougher, but this change will be something of a 

 sacrifice in flying power. 



Again, when the wings are thus folded, the insect covers 

 less area and is less conspicuous and therefore more likely 

 to elude the eyes of birds or other enemies, Its legs, which 

 are light and weak, having been used merely for support, 

 need greater strength to enable it to crawl and jump. The 

 eyes are not required to be so keen and naturally may 

 become smaller, and as it leads a lazier life it becomes 

 more corpulent and clumsy. To make up for the loss of 

 flying power in the front wings, the hinder ones become 

 wider ; this necessitates their being folded when at rest 

 in order that the narrower front wings may completely 

 cover them. 



Let us now consider how the grasshopper would fare 

 in the endeavor to lead the life of the dragon fly. In the 

 first place, the grasshopper lacks the flying power requisite 

 to capture lively little insects on the wing It must have 

 both pairs of wings developed for active use ; and it can 

 afford to do this, as it does not need to have the front pair 



