I collected her on September 16th and she became an adult about a week later. The dark red instar is the adult, the orange instar is the subadult.

Can we say this is Phidippus cardinalis? My thinking:

P. clarus - Edwards 2004 says a gray venter bordered in black stripes is diagnostic. The adult appears to match this only when starved. Once sated, I don't really see it. The subadult clearly doesn't match this.

P. apacheanus - Edwards 2004 says the clypeus fringe is black, which it clearly is not.

P. pius - Edwards 2004 says that pius has less red than cardinalis. It's hard to imagine this spider with less red, and it does not match well P. pius posted on BugGuide. I'm having trouble ruling this one out though.

P. cardinalis - Appears to match the description in Edwards 2004, but it also seems to match P. pius well.