Synonyms and other taxonomic changes
Colias scudderii Reakirt, 1865
Fairly easily identified by rounded wing shape, yellow color (not orange, but sometimes white in females), usually relatively wide and bold dark borders of male (weak to absent borders on females). Underside usually less greenish than in C. alexandra, with spot in middle of hind wing usually more prominent and ringed with at least some pink, often with a bit of a satellite spot. Black dots below are absent. C. alexandra has more pointed wings, narrower dark border in males, spot on under hind wing is usually faint and only white (but rarely with some pink), and it is usually somewhat more common and occurs in a wider range of open habitats. C. alexandra larvae feed on Legumes.
Southern Rocky Mountains, central Wyoming to northern New Mexico. It seems to be most abundant in the San Juan Mountains of New Mexico and Colorado, where it is sometimes the most common yellow butterfly at high elevations.
High elevation meadows and open sunny bogs near Willows. Usually associated indirectly with Spruce-Fir forest or Lodgepole Pine forest.
adults mostly in mid to late summer.
Larval hosts are Willows (Salix species)
Colias gigantea is very closely related, and perhaps these are merely regional subspecies of one species. C. gigantea replaces C. scudderi northward from Wyoming. It differs little, except averages perhaps a bit larger, and males have the dark borders somewhat narrower. They do not occur together, so they can be distinguished by location.
Reakirt, 1865. Observations upon some American Pierinae. Proceedings of the Entomological Society of Philadelphia. 4 (2): 217