The best pesticicides for ants include the chemical pyrethrin.
But a bit of investigation and a few tin cans can also be effective. Find out where the ant nests are place a tin can over it. The ants will then move most of the eggs into the tin can because it is hot. In mid afternoon, slide a piece of paper or card under the can and throw the eggs away.
Not sure if it works for red ants, but for regular ants I sprinkle grits over the nests, and wait for the ants to carry them down into the warren. Then pour the boiling water - which causes the grits to expand - closing off the tunnels.