Best treatment for ants outside is Termidor, hands down. It is like a liquid bait and any ants that walk over where you sprayed will pick up the Termidor on their bodies and transfer it to all of the other ants in the colony. Typically, within a few days to a week all of the ants will be dead.
Termidor can be used OUTSIDE only and is sprayed around the perimeter of your home. It is applied using a pressurized sprayer and the label suggests that it be sprayed twice yearly for ant control.
Directions for perimeter pest control are on the last page of the product label.
Here is a link to the Termidor product: http://www.domyownpestcontrol.com/termidor-sc-p-184.html
There are many reviews from our customers that have had great success with Termidor for ants on the Termidor page.