82 GEOTE — SPECIALIZATIONS OF LEPIDOPTEKOUS WING. [Jau. 21, 



scendants have existed and that forms, which have retained the ini- 

 termediate character and thus represent an earlier condition, may 

 yet be found and correctly identified. So that we must seek out 

 forms whose main disparity consists in their respective state of 

 specialization of the wings. 



Referring to the accompanying phylogenetic table, we may com- 

 mence our brief study with the so-called ''Yellows." In Eury- 

 mus (Colias) the second branch of the radius has passed from its 

 normal position before to one removed beyond the cross-vein. In 

 Meganostoma this branch has only progressed to a point opposite 

 the cross-vein. Clearly, Eurymus is the more specialized and 

 younger form since this passage of iiia along the main branch of the 

 radius is one indicated on different phylogenetic lines and is evi- 

 dently a phase of general process by which the radial branches are 

 reduced in number. The normal five-branched radius has this 

 branch, following iiii, before the cross-vein. Under this view 

 Meganostoma is the representative of the primitive form of Eury- 

 mus. The '' dog's head " pattern has probably yielded to the ter- 

 minal band, straightly margined and the reappearance of the 

 ''dog's head" in species of Eurymus is due to "reversion." In 

 other words, such species are the more generalized. But, while in 

 the type, hyale, the distance which the vein iiij has traveled is a 

 considerable one, it is much reduced in another species, edusa}, 

 which is more generalized in this way than E. hyale. From the 

 multiplicity of species of Eurymus, especially in North America, it 

 is not improbable that intermediate grades occur uniting the ex- 

 tremes E. hyale and M. ccesonia. I have not yet found them and 

 Eurymus is yet separable from Meganostoma on this character. 

 For purposes like the present study it is immaterial, so far as the 

 use of the two generic names is concerned, whether such forms are 

 found or not. The systematist needs both terms to designate dif- 

 ferent grades of specialization. The change in pattern involves a 

 loss of black and not improbably does there exist a tendency, in the 

 direction of specialization, to lose this and perhaps other darker 

 colors upon the same immediate lines. 



It is hardly probable that Callidryas is on the direct line of Eury- 

 mus, but it represents, in the holarctic fauna, an ancestral phase of 

 development. It has the same four-branched radius, but vein 



1 Mr. Mey rick's figure of ediisa (^Handbook ^ 35o) is too inaccurately drawa 

 to be of service. 



