BUTTERFLIES OF THE DISTRICT OF COLUMBIA 55 



survive the winter northward over the territory in which the sum- 

 mer brood is found, and that this migration is performed by widely 

 scattered individuals acting independently of one another. So far 

 as I have been able to ascertain there is no real evidence of any 

 northerly migration in spring. Individuals that have come out of 

 hibernation are commonly faded and putty colored. They seem to 

 have lost the energy that was theirs in the autumn, and fly with con- 

 tinuous wing beats within a few inches of the ground or of the grass 

 tops. They are so inconspicuous as to be easily overlooked, and 

 although I have kept a careful watch for them I have never seen 

 more than half a dozen. But all that I have seen were females 

 searching for plants on which to lay their eggs, and their actions 

 were quite the same as those of ovipositing females in summer. 



Yet occasionally individuals which have hibernated seem to be 

 possessed of full vigor. In the spring of 1931 two were reported 

 flying high in the air westward up the Potomac in exactly the same 

 manner as in autumn and in the same direction. 



Individuals which have hibernated have been found as far north 

 at least as Boston and Amherst, Mass., in the first half of May. 

 Farther south there are many records of hibernating individuals 

 in May. 



In this region fresh butterflies first appear early in June, and they 

 appear at approximately the same time in New England. 



The truth of the matter seems to be that a few scattered individuals 

 succeed in surviving the winter as far north as southern New Eng- 

 land on the eastern seaboard, and generally speaking everywhere over 

 the territory in which this butterfly is common in summer. From 

 the numerous eggs laid by these few individuals the early-summer 

 brood is derived, and from the eggs laid by the early-summer brood 

 come the very numerous individuals of the late-summer brood. 



It must be remembered that this butterfly is singularly free from 

 attack by parasites in the early stages, and also that the pupa, like the 

 adult, seems to be possessed of unusual vitality and to be able to 

 remain dormant for a considerable period, promptly giving forth 

 the butterfly when the conditions become suitable. 



According to W. H. Edwards the pupal stage, in southern West 

 Virginia, lasts from 5 to 15 days, but in one case he reported it re- 

 duced to 2 days. Mr. Scudder said that in New England the pupa 

 usually hangs for about 12 days, ranging from 9 to 15, but that he 

 has known it to be extended to 3 weeks. 



Relatively free from attacks b}^ parasites and possessing unusual 

 vitality in the pupal and adult stages, this insect has potentialities 

 for increase which are much in excess of those of most of our other 

 butterflies. 



66544—32 5 



