450 KEPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 



discrimination to any insect of the group that happens to become un- 

 pleasantly numerous in any locality. The following item, reported in 

 the Cincinnati Gazette of the 24tli of October, 1876, from Dayton, Ohio, 

 and referring in reality to the American Acridium, may be cited in 

 illustration : 



The advent of Kansas grasshoppers, over Sunday and until Monday evening, in 

 great numbers throughout the city, is a most remarkable incident. They were found 

 early Sunday morning, and left as suddenly as they came on Monday evening. 



Such reports are well calculated to mislead, by confirming the unsci- 

 entific m the belief that the "Kansas grasshopper" has overstepped the 

 eastern limits which, in Chapter YII, we have been at some pains to de- 

 fine. Even one of the governors present at the conference at Omaha 

 was fully imbued with the idea that the Rocky Mountain pest had come 

 all the way from Asia. 



"To the unscientific mind there are few things more difficult of ap- 

 prehension than that species, whether of plants or animals, should be 

 limited in geographical range to areas not separated from the rest of the 

 country by any very marked barriers or by visible demarkations. Yet 

 such is the fact, known to every naturalist, and the geographical distri- 

 bution of species forms at once one of the most interesting 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. Ttiese limits may, in fact, for the purpose of illustration, 

 be likened to those which separate d liferent nations. Though frequently 

 divided by purely imaginary lines, the nations of Burope, with their 

 peculiar customs and languages, are well defined. Along the borders 

 where two nations join there is sometimes more or less commiuglingj at 

 other times the line of demarkation is abrupt, and in no case could emi- 

 grants 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 su- 

 premacy 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 uninfluenced either directly 

 or indirectly by civilized man." 



We. hope that the full definition of the species most closely allied to 

 the Rocky Mountain pest, and the facts as to the home and geograph- 

 ical range of this last, which we have given in Chapters V and VI, 

 vill tend to set the public mind right on this interesting subject, be- 



