Bite Marks!!!

Yes, those are Maggie's teeth prints on Kate's arm... help! Just when I have begun to fully realize how difficult one 2.5 year old can be to keep in line (mainly because she is now refusing to take her MUCH NEEDED afternoon nap), the little ones are starting to attack. I'm sure it was purely a frustration thing on Maggie's part because she was riding peacefully in the boat, and Kate tried to overtake her. Kate got the nice bite marks as a result. However, I don't know what to do at this stage for discipline?!? Ella was very easy at this age because there was only one of her, and we only had the occasional play date. Now everyday is a play date at our house, so what am I to do? I have heard lots of talk about Love and Logic so I've got their Early Years book on hold from the library. Guess I should instead be reading up on how daycare centers handle discipline with 13 month olds! In the mean time, I'm just trying to watch them like a hawk! Any other suggestions?