CHAPTER II 

 HOW ANIMALS ARE CLASSIFIED 



The various insects we have described resemble one 

 another in different degrees so that it is possible to arrange 

 them in groups according to their degrees of likeness. 

 This process of grouping is called classification. For 

 many purposes it is desirable to divide various kinds of 

 objects such as books into classes and this is especially 

 desirable in the case of animals and plants of which there 

 are such vast numbers of different kinds. Animals or 

 plants which very closely resemble one another, and which 

 are commonly spoken of as belonging to the same kind 

 constitute what is called a species. For instance, the in- 

 dividuals of the Rocky Mountain locust form one species; 

 those of the red-legged locust another. The Grizzly bear 

 is one species, the black bear another and the European 

 brown bear a third. While species is the last or smallest 

 group usually dealt with, we sometimes recognize smaller 

 groups within the same species, which are called varieties. 

 We commonly speak of varieties of corn, wheat, cattle, pigs, 

 etc., where the groups differ but slightly, and where one 

 is known to have been derived from the other, or where one 

 group shades into the other one. It is not possible to 

 draw a sharp distinction between species and varieties, as 

 Darwin pointed out a good many years ago, and there is 

 often difference of opinion as to whether a group should 

 rank as a variety or as a distinct species. 



Different species that closely resemble one another are 

 classed as members of a larger group called a genus; a 

 genus therefore is a group of similar species. Now it is 

 convenient to give every species a name just as it is con- 



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