1898.] GROTE — SPECIALIZATIONS OF LEPIDOPTEROUS WING. 33 



iiij has not moved at all from the original position within the cell. 

 It is thus more generalized than either of its associates. From 

 Callidryas-like ancestors may rather have sprung the curious form 

 Colias rhatn?ii, belonging to the genus Rhodocera, or again Gonep- 

 teryx of authors, but, according to Scudder, wrongly so referred. 



In this genus in which the wings have probably been transformed 

 by mimicry to copy the shape of a leaf, vein iii.^ keeps its original 

 place of exit before the cross-vein ; consequently it cannot have 

 been derived from forms among which this vein was shifting. It 

 must have been thrown off before Meganostoma-like forms appeared 

 and probably Callidryas represents very nearly its direct line of 

 descent. It is more specialized than Callidryas, not only in the 

 remarkable shape of its wings, but because it has lost by absorption 

 vein i of hind wings, the '' praecostal spur" of some writers, which 

 is still retained by Callidryas. The specialization runs in this 

 respect parallel with the branch Eurymus-Meganostoma. In the 

 latter genus a remainder of the vanishing vein i is to be seen which 

 has become lost in Eurymus. The specialization on this phylo- 

 genetic line of the typical '' Yellows " has not apparently developed 

 a three-branched descendant, at least in the holarctic fauna, and so 

 far as my studies now go. Nor have I yet found the five-branched 

 generalized form, which might represent its more remote ancestry. 



Turning to the next line of non-typical "Yellows," the 

 Euremini, we find the three-branched descendant reached in 

 Nathalis. This form has evidently emerged from four-branched 

 ancestors, represented in America by Eurema and Terias, forms 

 which so very nearly agree that I am even at a loss to distinguish 

 them. I make out vein viii of primaries to be quite distinct and 

 relatively strong in Terias, and conclude this may be the sub- 

 speciahzed form of the two. I cannot now connect this line with 

 the typical *' Yellows," and its ancestry must be apparently sought 

 for in more southern regions. 



We will now take up the '' typical Whites." The three-branched 

 condition is attained by Mancipmin brassicce. Here the little remain- 

 ing branchlet iii34.4 of Pieris has at last vanished. But the vein iii3+4^5 

 in which it has lost itself is a little bent at this place. I should not 

 wonder if examples of the "large Cabbage White " might be found 

 retaining some trace of this vanished veinlet. In Pieris I have 

 examined rapcE and napi, while Prof. Comstock's beautiful figure of 

 protodice appears to agree (yEvoluiio)i and Taxono?ny, PI. ii. Fig. 3). 



PROC. AMER. PHILOS. SOC. XXXVII. 157. C. PRINTED MAY 18, 1898. 



