97 



I have no information as to the month in which Virginic7isis 

 has been taken in any northern or western locahty, except in the 

 one instance spoken of, when Mr. Mead captured a female, which 

 was in the last week of June, 1873, in the Catskills. This was un- 

 doubtedly one of the first generation. (Stony Clove has an eleva- 

 tion of 2,500 feet, and the trees there are not fully in leaf before 

 June.") Mr. Mead set this female in a bag on the food plant and 

 obtained many eggs. In a letter dated July loth, he says he 

 had then but one larva, one quarter grown, which would be after 

 the second moult. July i8th, he had sent the chrysalis from this 

 larva to Miss Peart for a drawing, and the drawing I have. Mr. 

 Mead informs me that from this chrysalis emerged Oleracea. 



We must conclude, therefore, that Virginiensis is an offset of 

 Oleracea hyemalis. It is singular that it should be so, differing 

 as this form does from hyemalis in the delicacy of the wings, their 

 pure ivJiite color beneath, and in the paleness of the yellow humeral 

 border. All which is in direct contrast to hyemalis. So the wings 

 are narrower than in hyemalis, and the gray brown dusting and 

 bordering of the nervules is in strong contrast with the same 

 form. It would seem in several respects more likely to have 

 come from cestiva. In West Virginia, this form Virginiensis is 

 also of the winter generation, and breeds true to its type, as 

 appears by all the examples taken during a series of years. As I 

 have said before, it has no second brood in Virginia. The offshoot 

 of a polygoneutic species has become single-brooded or monogo- 

 neutic. This is probably the result of climate. Oleracea, Napi, 

 Bryoniae, all are northern forms. The fauna of this region is 

 southern, whether botanical, ornithological or entomological, or at 

 least much more southern than northern, and the long hot sum- 

 mers are not favorable to this Pieris. The mild winter permits a 

 modified form, more like the summer generations of the north than 

 the winter generation, and this is held true to type by there being 

 no second brood. 



The first or original winter form. Bryonies, was left in the sole 

 possession of its arctic territory, after, by its southward emigra- 

 tion, a climate had been reached which allowed two annual gen- 

 erations to mature, and what then began as the summer form 

 ended by displacing its parent over the sub-boreal regions, and 

 itself became the second winter form, Venosa; developing a sec- 

 ond generation of its own. Pallida. But, collaterally, through 

 Oleracea hyemalis comes Virginiensis which along the southern 

 limit has in its turns displaced Venosa, being in sequence of de- 

 rivation the third winter form. But this has no second generation, 

 and in habit is like an Anthocharis, in which genus the butterflies 

 appear in spring, and have no second brood, all the chrysalids 

 going over to the next year. In fact, Virginiensis has parted com- 

 pany with Venosa and the rest, and has become a true species, 

 although unquestionably, in a higher latitude, it appears as an 

 occasional aberration only of Oleracea. 



