For carpenter ants we use a bait product called "Revenge" that we got at Agway in Gilford. It is simply boric acid mixed in a clear sugar syrup. Small amounts are placed on small cardboard squares and you let the ants eat. After about a week the ants will disappear.
The worker ants bring the mixture back to the nest to feed the queen and the larva. The boric acid does them in and wipes out the whole nest. You just have to get used to encouraging all those worker ants to eat-up for a few days.
