We had that problem two summers ago. We had had company who had seen a couple of very large ants in our guest bedroom. After they left (thankfully) we tore the bed apart and there were hundreds of them under the bed. We sprayed and sprayed and then as I was walking out of the room I noticed some more coming from under the door jamb. DH pulled the moulding off and there thousands of them under the wood. After a ton more spraying, and spraying all around the outside of the house, we finally got rid of them, thank heavens. It is no fun to battling those little devils.