THE Sl'HKAI) (»!•■ A HUTTKKKLY IN A NEW REGION. 1189 



knows how iniicli longer. Specimens were first brought east by Mr. A. 

 Agassiz in 1859. It is well known that tin- butterflies (not to mention 

 other animals) of the Pacific coast are more nciirly allied to those of the 

 Old World tlian are the butterflies east of the Koeky Mountains ; and there- 

 fore to one regarding these western Pierids as identical with P. rapae they 

 may well be looked upon as autochthonous, inasnuich as in the Old World 

 P. rapae extends from the Atlantic to the Pacific, from Great Britain and 

 Harbary to Kamtschatka and Jaj)an. 



My own belief, however, is that wc have in America, in addition to the 

 introduced P. rapae, two distinct autochthonous species, each of which shows 

 seasonal dimorphism similar to that of P. rapae and at least one of them some 

 marked geograi)hical races. If P. rapae and P. napi are distinct species, 

 as they are universally considered in Europe, then the American species, 

 previous to the introduction of P. rapae into eastern Canada, were distinct 

 from the European and from each other. That certain forms of each of 

 them, and especially of the western P. venosa, might readily be taken (as 

 has been done) for P. rapae is unquestionable, and it is possible that the 

 species seen in 1M84 and again in 1886 at Great Falls and the Belt Moun- 

 tains, Montana, was P. venosa, so marked. I have accordingly covered 

 the area upon the map over which P. venosa is known to extend with close 

 cross ruling, and that which it may probably also occupy with moi'e open 

 ruling. It will thereby be seen that the introduced P. rapae is rapidly 

 progressing toward its near of kin. It may well be believed that if P. rapae 

 has in the last five years crossed the high [)lains of Kansas and Nebraska on 

 its westward march, as it has done, the butterfly considered by others 

 as Pieris rapae, which has been on the Pacific coast since 1859 would, in 

 more than a quarter of a century, if it were P. rapae, certainly have ex- 

 tended eastward across the less arid country along the northern boundary 

 of the United States to a proportionably longer distance, — which it cer- 

 tainly has not done. It therefore fails in one characteristic of that raven- 

 ous and destructive species. It should be added that the only forms 

 considered by any one as identical with P. rapae are those described by 

 myself as P. marginalis and by Mr. Reakirt as P. yreka. They came 

 from California, Oregon and Washington Territory. 



With regard to the nature of the documentary evidence upon which 

 this account is largely based a few words may be said. One would expect 

 that much might be learned from agricultural and horticultural journals 

 about the movements of the butterfly, but a great amount of time has here 

 been wasted in vain search ; very little was to be found and that little 

 generally so vaguely stated as to be valueless. Direct enquiry has been 

 almost the sole resource of value after the entomological journals, and 

 especially the pages of the Canadian Entomologist. 



In the mass of information received from very various quarters in reply to 



