We had this not so unusual problem of hundreds of thousands of ants marching through the house, the front porch and side yard. They were clearly up to something big (a siege?) and we left them on their own for a couple of days. Their business was still unfinished. Nisha got tired of being up against an ant hill every day came up with a solution.
She cut a few small pieces of fresh lemon and placed them at critical junctions. In under 2 minutes, all but few had retreated to their bastion.
Later I googled and found that lemon juice is an ant repellent. But extracting the juice doesn’t seem to be necessary. And the lemon pieces are re-usable just in case the ants decide to re-route.
This has worked 5/5 times for us on small black ants and small red ants. Wait till they evolve!