34 ZOOLOGY. 



are generally found to the southward, this statement applying more par- 

 ticularly to the Coleoptera and Lepidoptera. It is only within the last few 

 years that anything has been known of the insect fauna of the Rocky Mount- 

 ain range proper and the area west of it ; and, as our knowledge increases, 

 we will possibly be better able to establish a theory or theories of develop- 

 ment, distribution, and color-variation, which will aid in establishing a gen- 

 eral law, applying to all classes of animated nature. 



Thanks are due to Professor Allen for his kindness in permitting the 

 use of his papers already mentioned, and for his criticism of this chapter. 



