_Egg._--The egg is spindle-shaped, thickest at the middle, tapering at the apex and at the base, generally attached by an enlarged disk-like expansion to the point on which it is laid. The upper extremity is rounded; the sides are marked by small vertical ridges, between which are delicate cross-lines. _Caterpillar._--The caterpillars strongly resemble in appearance those of the preceding genus, from which, superficially, they cannot be distinguished by any anatomical peculiarities. They feed upon _Leguminosæ_, and especially upon clover (_Trifolium_). _Chrysalis._--The chrysalids do not generally differ in appearance from the chrysalids of the genus _Meganostoma_, though the wing-cases do not form as high a keel-shaped projection from the ventral side as in that genus. This genus is very extensive, being represented throughout the temperate regions of both hemispheres, and also occurring in the cooler portions of South America, especially along the ranges of the Andes. One species is found in temperate South Africa. The brightly colored butterflies, which are sometimes found congregating in immense numbers in moist places, are familiar objects, and swarm upon the clover-fields and by the roadside in the summer months throughout the United States. (1) =Colias meadi=, Edwards, Plate XXXVI, Fig. 5, ♂; Fig. 6, ♀ (Mead's Sulphur). _Butterfly._--The wings on the upper side are orange, greenish on the under side. The discal spot on the lower side is centered with green. Expanse, 1.75 inch. _Early Stages._--The life-history has been written by Edwards, and may be found in the pages of the "Canadian Entomologist," vol. xxi, p. 41. The larva feeds on clover. The species is alpine in its habits, and is found in Colorado from nine to twelve thousand feet above sea-level. (2) =Colias elis=, Strecker, Plate XXXVI, Fig. 13, ♂; Fig. 14, ♀ (Strecker's Sulphur). _Butterfly._--This species is discriminated from the preceding principally by the narrower black margins on the wings of the male and the more abundant yellow maculation of the borders in the female. Expanse, 1.55-1.90 inch. _Early Stages._--Closely resembling those of the preceding species, of which it may be only a varietal form. The habitat of the species is on the lofty peaks of the Western Cordilleras. (3) =Colias eurytheme=, Boisduval, Plate XLVIII, Fig. 18, ♀; Plate XXXIII, Fig. 5, ♂, _under side_; Plate II, Fig. 1, _larva_; Plate V, Fig. 53, _chrysalis_ (Eurytheme). _Butterfly._--This species has been made in recent years the subject of exhaustive study, and has been discovered to be strongly polymorphic--that is to say, liable to great variation. Not only does albinism assert itself in the production of white forms, but there are many seasonal and climatic forms. We are not yet through with our studies, and there is doubtless much more to be ascertained. The figures cited above represent the typical form of the species. We have given, in addition to these, the following forms: