NYMPIIALINAE : BASILARCIIIA PROSERPINA. 291 



astyanax where this prevails, and most toward arthemis where that 

 prevails. 



3. A careful comparison of a considerable series shows that there is no 

 difference whatever in the genital armature of proserpina and astyanax. 



4. Proserpina varies more than either of the supposed parents and 

 approaches astyanax so closely that one with so keen a perception of super- 

 ficial distinctions as Mr. Edwards, cannot determine of certain specimens 

 whether they should be classed with astyanax or with proserpina. Speak- 

 ing of nine specimens sent him from Milford, N. H., Mr. Edwards says : 

 *'The first three spoken of I have no doubt are true proserpina, and 

 probably all the others are, though they cannot be distinguished from some 

 exam})les of Ursula [astyanax] , taken in certain districts where arthemis is 

 never known to fly. . . . Therefore, I cannot say that all these Milford 

 examples are not proserpina ; and, indeed, I do not know where proser- 

 pina ends and Ursula begins, though a tyjiical example of each is distinct 

 enough." (Butt. N. A., ii.). 



5. Proserpina occurs only in a very narrow belt across the eastern 

 third of the continent — a belt which forms the southern boundary of the 

 range of arthemis and the northern boundary of the range of astyanax. 



6. Proserpina is known at so many points in this belt, that it presum- 

 ably occurs wherever arthemis and astyanax are brought into contact. 



7. Although regional dimorphism is known in many instances, there is 

 no dimorphic butterfly known in which one of the forms is wholly limited 

 to the confines only of its regional distribution and at the same time 

 extends over a long distance ; nor, so far as I am aware, has any such 

 case been recorded among other dimorphic animals. 



There are but two arguments used to prove the improbability of such a 

 relationship as is here urged : 1°. To assert that proserpina occurs in some 

 districts ^vhere astyanax is not found, but occurs in no districts where 

 arthemis is not found. 2°. That specimens which had once been looked 

 upon as proserpina, are a northern form of astyanax Avhich, in a belt of 

 "several degrees of latitude," lives "side by side with the southern 

 form." 



As to the first, there is but a single place where proserpina has been 

 found, where it is probable that astyanax does not occur within at least an 

 easy day's flight ; a distance of a few miles is of no account whatever. 

 Hamilton, Ontario, is on the same parallel as London and Rochester, and 

 only seventy-five miles from the former. Portland, Me., is at no greater 

 distance from the more elevated, and but slightly more southern localities 

 in New Hampshire, whence astyanax is known. The only place that need 

 concern us in Halifax, N. S., three hundred and fifty miles from the New 

 Hampshire coast, from which in a single instance, nearly twenty years ago, 

 proserpina has been reported, of which Mr. Edwards wrote in 1870 : "I 



