III. The Intkoductiox and Spread of Piehis kapae in North America, 

 1860-1886. With a Map (Plate 8). 



By Samuel H. Scudder. 



(Read May 4, 1887.) 



J_T is well known that the different races of men have not always occupied the regions 

 which they now inhabit, bnfe that from the eailiest times one wave of migration has fol- 

 lowed another, in a manner that has proved very pei'plexing to the ethnologist attempt- 

 ing to follow them. That the lower animals also have had their migrations has been 

 frequently proved by the occurrence of their remains in regions where they are not now 

 found. Secular change of climate has been the great moving cause of most of the 

 migrations of which we have any knowledge, with the single exception of the influence 

 of man, and particularly of civilized man; he is everywhere upsetting the arrangements 

 of nature, directly or indirectly exterminating all forms which cannot endure his pres- 

 ence or withstand the baleful influences which follow in his train. To minister to his 

 wants, for instance, he brings into a new region a plant foreign to its soil that he may 

 have the fruit ready to his hand. Without the natural hindrances which prevent its 

 supremacy in its native home, it thrives so vigorously, if otherwise adapted to the place, 

 as to supplant the natural denizens of the soil; these are supporting numerous animals, 

 which in their turn suffer. 



So it has doubtless been in all ages of the world, where by any of the multifarious 

 means which nature employs she has herself upset the balance she had established, by 

 bringing into a flora or a fauna some new element from without. Indeed, the history 

 of animal and plant life has been a story of colonization. Any one who has observed 

 the rapidity with which weeds spread over new countries, has read of the ral)bit nui- 

 sance in Australia or seen the sparrow nuisance in America, will comprehend what a 

 force colonization may have been. It was closely linked no doubt Avith the introduc- 

 tion of new types in past ages of the world. 



The measurement of the sjjread of a newly introduced sjiecies has rarely been at- 

 tempted. Indeed, in the nature of things it could scarcely ever be made except under 

 circumstances which may fairlj' be deemed artifleiaj, i. e., in countries tolerabi}' well 

 settled with people intelligent enough to report accurately. Karcly, too, is the date of 



MEMOIRS BOSTON SOC. NAT. HIST., VOL. IV. 8 (53) 



