THEORIES OF EVOLUTION 123 



cumpolar skipper, Pyrgus centaureaeJ This insect 

 is found in northern Europe and North America, 

 and extends in the mountains as far south as 

 Colorado. It has been taken in New Jersey at 

 Great Notch, and is fairly common in Labrador. 

 In these and the intervening eastern areas it occurs, 

 necessarily, at fairly low altitudes, but in Colorado 

 it is found on high mountains. I have had it from 

 an altitude of 13,000 feet. Labrador specimens 

 are not unlike Colorado specimens. The New 

 Jersey specimens that I have seen are rather dis- 

 similar in appearance. Specimens from Lapland 

 are much like those from Labrador, Colorado, and 

 various parts of Canada. There is no available 

 evidence for regarding this assemblage of insects 

 as more than one species; certainly, according to 

 the accepted views of all entomologists, one species 

 extends over the entire area even though it may 

 be associated with another. Yet there is a rigid 

 isolation of some individuals on the Colorado 

 mountains and on the two continents and an actual 

 isolation with indirect association between the 

 individuals occurring in the east and at higher 

 latitudes. The future development of the species 

 in Colorado must obviously be based on the char- 

 acteristics of the original stock of that region, while 

 its development in New Jersey may be based on 

 an originally different heritage. 



' Ent. News, Vol. XXXIX, pp. 239-241, 1928. 



