We have those here, and commonly, in Arizona. Their common name here is the Sun Spider. They are an arachnid.
My first sighting of them was this: I was a bit homeless a few years back (long story), and my boss let me use his spare apartment. As I woke up in the morning, I would see hundreds of what I thought to be newborn scorpions dashing around. After about 4 days of this, I finally woke up to a HUGE Sun Spider sitting on my pillow just about to walk on my face.....
So I took this big girl (I figured so much, because this is what turned out to be the same species as the hundreds of babies) and went to study what it was. I knew another Arizona resident up close and personal.