202 The Rocky Mountain Locust. 



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 two nations join, there is some- 

 times 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 is 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 from natural agencies, while those 

 of species result chiefly from the latter, and are therefore 

 more permanent. These remarks apply of course to 

 species in a natural state, and where their range is unin- 

 fluenced either directly or indirectly by civilized man. 



I found some difficulty, at the Conference of Governors 

 at Omaha to consider the locust problem, in satisfying 

 those present that the Rocky Mountain Locust could not 

 permanently thrive in the country indicated by green in 

 Plate I. of this work, 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 center of Iowa. They could 

 not see what there was to prevent the pest from overrun- 

 ning the whole country, and thought that Congress should 

 be appealed to, not only on behalf of the country that 

 has suffered from its ravages, but on behalf, also, of the 

 whole country that is threatened thereby. 



Having already discussed the native home of the species, 

 and the conditions which prevent its permanent settlement 



