142 The Classification of Insects 



spondence with the ever-changing conditions and 

 needs of its life. 



The theory of natural selection, by furnishing 

 a reasonable explanation of how the evolution of 

 species might be brought about, has led naturalists to 

 abandon belief in the independent origin of different 

 kinds of animals, and to embrace the view that all 

 living creatures are really related to each other. The 

 origin of species is shown to be a problem capable of 

 solution, to some degree at least, by patient observa- 

 tion and reasoning ; and man, no longer content with 

 merely giving names to the living creatures around 

 him, begins to ask how they come to be as he finds 

 them. But though the Darwinian theory has led to 

 the universal acceptance of the evolution doctrine by 

 scientific men, the greatest divergence of opinion still 

 prevails as to the value of that theory in explaining 

 the differentiation of species. While some write of 

 the " all-sufhciency of natural selection" (57)> others 

 deny that specific differences are in any way due to 

 its influence (89, 93). 



Utility of Specific Characters. — The reality and 

 severity of the struggle for existence cannot be denied, 

 nor is it possible to doubt that a rigorous selection 

 among both individuals and species results from it. But 

 if specific characters have become fixed by the action 

 of this selection, these characters must be of use to 

 the animals possessing them. The strongest reason 

 for doubting that natural selection is the *' all- 

 sufficient " cause of the origin of species, is that the 

 characters which distinguish species from each other 

 seem often of no use to their possessors. 



For example, there are two nearly-related species 

 of small Beetles often to be found abundantly in stores 

 of flour and meal, on which both the beetles and their 

 grubs feed. They are about a sixth of an inch long, 



