I have a potted Pachypodium in the windowsill with an ant nest in its soil. A couple of months ago I left it in water for a week and thought I had got rid of them, but a new batch must have hatched or returned. When I soak the soil both normal looking ants carrying eggs and apparently flightless ants with wings emerge. What should I do to convince them the plant is not a good place to live?
If these are sweet-loving ants, there's a product called Terro that you can use - it's essentially boric acid mixed with Karo syrup. The ants feed on the syrup and bring enough boric acid back to the next to kill the queen.
If the pot isn't too heavy to move, I'd probably first move it outside, unpot the plant, and remove the soil (and hope the ants don't bite too hard). I'd probably wash as much soil from the roots as needed to remove the ants - you're really looking for the queen. Once you remove the queen, the rest of the colony will either move with her or die.