86 THE CANADIAN ENTOMOLOGIST. 



four inches high. On 27th May, I found a pupa hanging to the outer side 

 of a rail, as I crossed the railway to my garden. I then, in the fall, 

 searched daily for eggs, to see how late they were to be found. On 2nd 

 Sept., I found 2 eggs ; on 4th, 1 ; on 8th, 1 ; on 10th, 1 ; on 14th, 1, and 

 saw the female lay this egg; on 16th, found 3 ; on 20th, 2 ; on 22nd, 1. 

 I found no eggs later than this. Mr. Marsh found larvae up to 30th Sept., 

 though he obtained no eggs apparently later than 5 th Aug. But the eggs 

 to produce his late larvae must have been laid early in September. On 

 26th and 27th Sept., I had occasion to drive many miles, and saw great 

 numbers of the fresh butterflies flying about the Actinomeris flowers. My 

 last imago, from one of the eggs found, was 12 days in pupa and came 

 out nth Oct. So that the butterflies were coming out of pupae later, if 

 anything, at Amherst than they were at Coalburgh. 



It had been said that no one ever found an Archippus egg in New 

 England, or on very young Asclepias plants, that could have been laid 

 by an hibernator, though thousands of plants had been searched, at 

 different localities, by many persons. Negative evidence is no evidence 

 at all in such a case. If one thousand plants had failed to produce an 

 egg, the one thousand and first plant nevertheless might have it. The 

 hibernated females are very few, as there is every reason to believe, after 

 hearing of the wholesale destruction over large areas of country of the 

 late larvae ; and Asclepias plants are exceedingly plenty in the spring, 

 thousands of them to one Archippus egg, no doubt. So that a person 

 might very possibly look all day and not find an egg. And on the other 

 hand, the first plant touched might have an egg on it. That the eggs 

 are there is sufficiently proven by the resultant butterflies. 



ON THE NATURE OF SEASONAL DIMORPHISM IN 



RHOPALOCERA. 



BY T. D. A. COCKERELL, WEST CLIFF, COLOKADO. 



In studying the seasonal variation exhibited by various species of 

 butterflies, I have been struck by the fact, that whereas in most instances 

 the form emerging in the spring is darker and smaller than the summer 

 brood, there are also exceptions to this rule, in which the vernal emer- 



