﻿82 NINTH ANNUAL REPORT 



graphical distribution of species forms at once one of the most inter- 

 esting and one of the most important studies in natural history. 

 Some species have a very limited, others a very wide range ; and 

 while in the course of time — in the lapse of centuries or ages — the 

 limits have altered in the past and will alter in the future, they are, 

 for all practical purposes, permanent in present time. These limits 

 may in fact, for the purpose of illustration, be likened to those which 

 separate different nations. Though frequently divided by purely 

 imaginary lines, the nations of Europe, with their peculiar customs 

 and languages, are well defined. 



Along the borders where the nations join, there is sometimes more 

 or less commingling ; at other times the line of demarkation is abrupt ; 

 and in no case could emigrants from the one, long perpetuate their 

 peculiarities unchanged in the midst of the other. Yet in the battle 

 of nations, the lines have changed, and the map of Europe has often 

 been remodeled. So it ic with species. On the borders of the areas 

 not abruptly defined, to which species are limited, there is more or 

 less modification from the typical characters and habits ; while in the 

 struggle of species for supremacy, the limits may vary in the course 

 of time. The difference is, that the boundaries of nations result from 

 human rather than natural agencies, while those of species result 

 most from the latter, and are threfore more permanent. These re- 

 marks apply of course to species in a natural state and where 

 their range is uninfluenced either directly or indirectly by civilized 

 man. 



I found some difficulty at the late Conference of Governors at 

 Omaha to consider the locust problem, in satisfying those present that 

 the Rocky Mountain Locust could not permanently thrive south of 

 the 44th parallel, or ease of the 100th meridian, and that there was no 

 danger of its ever extending so as to do serious damage east of a line 

 drawn a little west of the centre of Iowa. They could not see what 

 there was to prevent the pest from overrunning the whole country;* 

 and thought that Congress should be appealed to, not only on behalf 

 of the country that has suffered fromits ravages, but on behalf also of 

 the whole country that is threatened therefrom. 



Having discussed in my two previous Reports the native home of 

 the species, and the conditions which prevent its permanent settle- 

 ment in the country to which it is not native, it is unnecessary here to 

 go into detail on these points. Briefly, the species is at home and can 

 come to perfection only in the high and dry regions of the Northwest, 

 where the Winters are long and cold and the Summers short ; and 

 whenever it migrates and oversweeps the country to the south or 



