You can get Boric Acid at the Dollar store (or any grocery) in the form of a roach killer. It's in a tall yellow plastic cylinder. Mix equal parts boric acid and powered sugar or something similar. (I did it recently and used a little bit of sugar cookie mix.) Put some in a lid or something that the ants can get into, place it near their trail. They will take it 'home' to feed the others and it will kill them off. Worked well for me outside this summer.