The Rocky Mountain Locust. 



But, it will be asked, " Upon what do you base this con- 

 clusion, and what security have we, that at some future 

 time the country east of the line you have indicated may 

 not be ravaged by these plagues from the mountains ? " I 

 answer, that during the whole history of the species as I 

 have attempted to trace it in the chronological account 

 already given, the insect never has done any damage east 

 of the line indicated, and there is no reason to suppose 

 that it ever will do so for the future. There must of course 

 be some limit to its flight, as no one would be foolish 

 enough to argue that it could, in one season, fly to Eng- 

 land or France, or even to the Atlantic ocean ; and as its 

 flight is by law limited to one season — for the term of life 

 allotted to it is bounded by the spring and autumn frosts — 

 so its power of flight is limited. And as the historical 

 record proves that it never has done any damage east of 

 the line indicated, it is but logical to infer that it never 

 will, so long as the present conditions of climate and the 

 present configuration of the continent endure. It is an 

 interesting fact that whether on the Gulf of Mexico or in 

 British America the eastern limit-line is approximately the 

 same. 



" But why," it will again be asked, "will not the young 

 from the eggs laid along the eastern limit you have indi- 

 cated, hatch and spread further to the eastward ? " Here, 

 again, historical record serves us, and there are, in addi- 

 tion, certain physical facts, which help to answer the 

 question. In Chapter V it is shown, that the young 

 insects do not reach, on an average, ten miles east of any 

 point where they hatch, and that upon acquiring wings 

 they fly in the main northwestwardly. 



East of color-line indicated in Plate I, they did not reach 

 in a general way, either in 1874 or 1876, and beyond that 

 line I do not believe they will ever do any damage. Not 



