14 



The Genus Eurymus (Colias), with Special Reference to 

 E. Eurytheme. 



By Hv. J. Turner, F.E.S. Read June 22nd, 1905. 



I am exhibiting a series of Colias eurytheme^ or, as it should be, 

 Eurymus eurytheme, from Assiniboia, sent to me by our member 

 Mr. Croker. This insect is very common all over North America, 

 and is one of the most variable of butterflies. Except during the 

 winter of the north or during the hottest summer in the south this 

 species in one form or another is to be met with almost everywhere. 



Many of its forms, when first discovered, have been described as 

 distinct species, or confused with other species, and only after the 

 long-continued observations of Edwards, Scudder, and others has the 

 identity of these been established. Even now there is probably 

 much still to be ascertained in a species with such an inherent ten- 

 dency to vary, and one that is spread over such a vast area. 



Scudder gives the following named forms of the species : Eurymus 

 eurytheme var. ariadne, the yellow southern form ; var. eriphyle, the 

 yellow northern form (a- different shade from the first) ; var. kee- 

 waydtn, the yellow orange type (orange suffusion from the base into 

 the disc) ; var. Christina ?, the form exhibited (yellow at base only 

 of all the wings); var. keeivaydin alba, pale form, corresponding to 

 var. helice of E. edusa ; var. amphidusa, the orange type, with no 

 yellow ; var. amphidusa alba, pale form corresponding to var. helice 

 •of E. edusa. 



Eurymus eurytheme has a polymorphism hardly exceeded by that 

 of any other butterfly. In the mountains of Colorado this species is 

 double brooded, and the imagines of the second brood hibernate. 

 In Illinois it is three-brooded, and both larvas and imagined hiber- 

 nate. In the lowland of California it is triple- or quadruple-brooded, 

 and the imagines only hibernate. In Texas the species aestivates as 

 a larva from June to October, when the clover pastures are dried up, 

 while the imagines are always to be seen from November to June. 

 So that here we have a species which can both hibernate and 

 aestivate, and its hibernation may be either in the larval or imaginal 

 stage. 



This species is distributed over an enormous area of country ex- 

 tending from the Atlantic to the Pacific, and from the borders of the 

 Gulf of Mexico to beyond the northern boundary of the United 

 States. Assiniboia, from which the specimens exhibited came, is on 

 the extreme northern edge of the area of its distribution, and hence 

 we might expect to find forms showing some distinctly aberrant 

 characters. 



