THE CANADIAN ENTOMOLOGIST. 53 



period the primary form, together with phaon and vesta, had made its way 

 southward, where all three are found now, and neither of them, so far as 

 appears, having developed any marked varieties of the winter form. 



[After this paper was written, and the first part of it in type, I received 

 from Mr. Boll a fine series of tharos, phacm and vesta, from Texas, with 

 the dates of capture accompanying each example. It appears that tharos 

 there flies from February to November, and there must be in all six or 

 seven generations during this period. Five of these are represented in 

 the series sent. All the examples of tharos are of small size, resembling 

 in this respect those from the far north. All, except the February 

 examples, which are var. B winter form, are very dark above, the black 

 intense and the fulvous deep red, and some of the males have the under 

 side of the hind wings almost deprived of markings of any sort, and to a 

 considerably greater degree than I have observed in more northern 

 examples. But certain males labeled Sept., Oct., resemble surprisingly 

 var. C of the Avinter form. I find the first of these phases, that of the 

 plain wing, also in phaon, and among the examples of this 

 species is a female labeled November, that is undoubtedly the 

 winter form, var. B, and which would be expected to appear in 

 February, after the winter. And this has led me to suspect, con- 

 sidering the effect produced on the Coalburgh larvs fed in the 

 Catskills, as before related, that a cool season during the time the fall 

 brood is feeding, or a few cool days after the chrysalis is formed, may tend 

 to change the form of such of the butterflies as will emerge before winter, 

 so that they shall not difter from those which pass the winter in chrysalis 

 and appear in February. That may happen naturally which was brought 

 about artificially with the Coalburgh brood spoken of 



 I have also received a letter from Dr. Weismann of i6th Nov., 1876, 

 which by his permission I may give in this connection : " Naturally your 

 experiments with tharos have greatly interested me. The case seems to 

 me perfectly intelligible \ viarcia is the old, primary form of the species, 

 in the glacial period the only one. Tharos is the secondary form, having 

 arisen in the course of many generations through the gradually working 

 influence of summer heat. In your experiments cold has caused the 

 summer generation to revert to the primary form. The reverting which 

 occurred was complete in the females, but not in all the males ! This 

 proves, as it appears to me, that the males are changed or affected more 

 strongly by the heat of summer than the females. The secondary form 



