Or Flower Bee? (Thanks, Richard!)
Either way, I can also thank LeftCoastNaturalist for this one, since before reading his blog post about Cuckoo Wasps (http://leftcoastnatty.blogspot.com/2014/05/cuckoo-for-chrysidids.html) I'd never heard of them, and after reading they've been buzzing around insistently but pleasantly in the back of my mind. I might not have noticed this little one otherwise. Thanks, Trent, and great blog!