So I found a whole colony of these on the side of one of my big containers. I believe they were disturbed when I dug up a dusty miller elsewhere; I'd set the pot I put it in next to this container, and watered it a little. When I moved dusty, these fellas were all over the side of the green pot.
I've been looking through bugguide.net but so far haven't run across this one so thought I'd see if it looks familiar to anybody.