If they are flea beetles, they can be very destructive to the plants that they like. They will mutilate eggplant leaves in only a few days if not controlled. Insecticidal soap helps, but Neem works even better.

I get some kind of little black beetle that chews up my plum and related trees each year. Well, the damage is actually done by their little grub/worm beforehand.

Thanks for the help. I'm still not sure what they were but they seem to have dispersed. They were all over the lamb's ear in the front bed, but whatever damage they did seems to have been minimal.