Best treatment for ants outside is Termidor, hands down. It is sort of a liquid bait when used for ants, and any ants that walk over where you spray pick up the Termidor on their bodies and bring the product back to the colony where they spread it around to all other termites, including the queen, and typically within a few days to a week all of the ants will be dead. Termidor is used around your home like any other pest control product and is applied using a one gallon hand pump sprayer. You should re-apply every 3 months for optimum ant control.
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.