34 DISTRIBUTION OF ANIMALS. [part i. 



mistaken for something else. Then again, insects have enemies 

 in every stage of their existence — the egg, the larva, the pupa, 

 and the perfect form ; and the abundance of any one of these 

 enemies may render their survival impossible in a country other- 

 wise well suited to them. Ever bearing in mind these two 

 opposing classes of facts, we shall not be surprised at the 

 enormous range of some groups of insects, and at the extreme 

 localization of others ; and shall be able to give a rational account 

 of many phenomena of distribution that would otherwise seem 

 quite unintelligible. 



