Not far from where I found the cellar spider last week, I found this caterpillar feeding on a small ironwood tree. Instead of being alarmed that a caterpillar was eating my plant, I was actually pretty excited. I was pretty sure it is the larval form of the Mexican yellow, a very pretty butterfly. If not, then it is a closely related species.
If you are interested, here is a link to the Butterflies of Southeastern Arizona page which shows what the caterpillar might turn into, the Mexican yellow, Eurema mexicanum.
And here is their picture of the larva stage. Do you think it is the same kind, too?
The caterpillar was over an inch long, probably nearly mature. The next day it was gone. Hopefully it crawled away to form a chrysalis in a protected place and I'll be showing you a photo in a few weeks.