In sandy habitat leading to the beach, I thought these were wasps looking for prey or a nest site by the way they were looking around on the sand. Two were together, then another came, and they were all rolling around. I thought it was a pair mating, with another male trying to interrupt them. On the way back from the beach, I found another one, at first glance with prey. Turned out it was dead, and a smaller ant was trying to deal with it. After I took the dead one home, I saw it had a petiole hump. The rear end looks the same on the dead one as the live one I got into a bug box, so I'm including those photos even though it isn't the same specimen.