+1 for Terro. About 24 hours after setting the traps, all but a few strays left.
Baby powder will work, too. Get Rid of Ants Cheaply and NaturallyAlso, put chalk dust (yes chalk like what the kids play with just ground up) in the back of your cabinets, in the groove of the outside door frames, and along the wall near any pet food. Ants won't cross the chalk and it is safe to have near food.
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I have the little ants in the yard. Now they are moving into the house. I put out the granules twice in the yard and now am probably going to have to do it again. I'll have to take action on the ones who are starting to come in through the garage and vents in the brick of the house.