THE TRIBE OF THE WHITES 87 



mention various others which have been found in Europe. 

 This is indeed a remarkable showing and it is a striking 

 illustration of the infinite variations which Natiu'e can 

 produce with the most limited materials. 



To me the seasonal variations of a butterfly are always 

 of greater interest than those which are geographical. 

 We know that in the case of a great many animals, from 

 insects to mammals, the different conditions of climate 

 and physical environment found in different regions pro- 

 duce variations of many sorts. So it does not seem es- 

 pecially strange that in Alaska there should be a different 

 form of a certain butterfly than is found in Virginia. But 

 that in the same locality there should be two or more 

 forms of a butterfly existing under identical conditions as 

 to climate and environment is not so easily explained. In 

 the case of the Gray-veined White we collect in early 

 spring in New England, or other Northern states, a lot of 

 chrysalids. We keep them until the butterflies come 

 forth and we find even here two distinct forms, one smaller 

 and more delicate than the other, with both surfaces of 

 the wings pure white : scientists call this form, virginiensis ; 

 the other larger with the under surface of the wings slightly 

 tinted with yellow: scientists call this form oleracea. 

 The first named has but one brood a year while the 

 second lays eggs which develop into caterpillars that 

 produce butterflies of still a third form, in which the 

 upper surface of the wings is pure white with a slightly 

 greater expanse: scientists call this form cruciferarum. 

 These three varieties occur in Eastern regions and may 

 be found in the same localities, and differ considerably 

 from various geographical varieties found in the Far 

 West. ' 



