To control ants here, I use boric acid, it is a powder, I put it along any entry way the ants may be or might use, if you use it outside of your doors, you will have to re-apply the boric acid powder after it rains or gets wet..

here is info on it:
http://alsnetbiz.com/homeimprovement/boric_acid.html
http://www.biconet.com/crawlers/boricAcid.html

If you choose to try this, do not put it in such a place that a household pet would have access to it, this stuff is a poison.. "Boric acid is generally known as a desiccant; in other words, it kills by removing the moisture from the body of the target pests, causing severe dehydration which will affect electrolyte metabolism with the potential of metabolic acidosis. In fact, boric acid is a stomach poison normally ingested, along with the fact that it can also enter the blood by inhalation. Boric acid is an acid. Acid will decrease the pH level with the possible side effects of renal, respiratory, and cardiovascular failure. Symptoms and signs of boric acid poisoning are nausea, vomiting, diarrhea, headache, dysphagia, cold sweats, dyspnea, muscular debility, scarlatinal eruptions, subnormal temperature, cardiac weakness, cyanosis, coma, collapse, etc. Boric acid is 3 parts hydrogen, 1 part boron, and 3 parts oxygen"