Clouded Butterfly Taxonomy

Two Clouded Sulphur (Colias philodice) butterflies

It's hard not to notice the big, yellow butterflies floating around these days. What's really hard is figuring out what they are. As a group, the yellow ones are called "sulphurs" (Colias spp.). One unusual sulphur behavior is that they never open their wings when they're perched - except when a female rejects a male's advances.

My book says that nine different species might be seen in Montana, only five in the western part of the state. The most common yellow sulphur is the "Clouded Sulphur" (C. philodice). But even the experts disagree on how to sort out all of the sulphur species. They haven't even agreed on how many sulphur species there are in the western U.S.

So if you remember to say, "Sulphur!" next time you see a yellow butterfly, you are doing well. And if you tell your friends, "Yep. That one's a Clouded Sulphur," they'll be doubly impressed. And they'll also be hard-pressed to prove you wrong.