174 THE CANADIAN ENTOMOLOGIST. 



of this yellow form run parallel with that of the orange, of which Ariadne 

 is the winter and Eurytheme the summer form. (In Philodice there is no 

 seasonal dimorphism discernible.)* 



Polymorphic forms of butterflies are especially interesting biologically, 

 for they may be regarded as species in the making. It is conceivable, 

 for example, that each one of these forms of Eurytheme, under certain 

 conditions, might become separated from the other, and breed true to its 

 own type. In other words, come to be a species, and I doubt not, very 

 many species of butterflies have come to be in this way. 



I have said that none of my bred males have had orange in the wings. 

 But I have two males, one taken by Mr. Morrison, in south Colorado, 

 the other by Mr. Nash, at Pueblo, which have a pretty strong shade of 

 the chrome color on fore wings that characterises so many of the females. 



Hagenii is known to fly throughout the Rocky Mountain region from 

 Colorado to British America. I had many examples from Mt. J^idith, 

 Montana ; others from Bismarck, Dacotah, and along the boundary line 

 of B. America, in same Territory. Mr. Morrison also brought exam- 

 ples from Montana, but I know not what part. So several have been 

 sent me from San Bernardino, by Mr. Wright and Mr. Hulst, and I think it 

 probable the yellow form accompanies the orange over much of the territory 

 occupied by the latter. On the plains to the east of the mountains, these 

 would have been regarded as Fk Hod ice by collectors. 



The yellow male figured in But. N. A., vol. i, on plate of Colias Kee- 

 waydin, fig. 7, is Hagenii, a very small example. Mr. Henry Edwards is 

 quoted in the text as writing that " the male of the new species (Keewaydin) 

 is constantly subject to run into the lemon-yellow variety." 



As to the larvae, they vary greatly ; some having no trace of a sub- 

 dorsal band ; others have a slight yellow line in place of band ; others 

 have decided yellow lines or narrow white bands. Not one of my bred 

 larvae has had a sub dorsal band with red in or running through it. On 

 the other hand, Mr. Nash has sent me several nearly mature larvag which 

 produced Hagenii butterflies, in which either the white sub-dorsal band 

 with red line through it was present, or a white band without red. In one 

 letter Mr. Nash writes : " Out of 24 nearly full grown larvae of this 

 Colias that I have, 14 have the sub-dorsal line, but none a distinct white 



* Mr. Nash informs me that form Ariadne often flies at the end of the season, at 

 Pueblo, the temperature having permitted the larvtv to mature. 



