I'd call it a "sweat bee" that appeared to be hovering an inch or two over the ground. Then I realized it was following an ant. The ant was carrying something and backing up like a lobster. The ant would retreat an inch, and the bee would follow.
This went on for about a minute and covered about 8 inches of ground. Then the ant backed up against a twig, apparently being cornered. The bee moved in, picked up the ant (and cargo as near as I could tell), and flew up about twelve feet, into the arms of a pine tree, and there I lost sight of it.
I wonder why a bee would carry off an ant. Curious.