There is a product named 'Terro" on the market that others who have
used it swear by, but I haven't used it. Is supposed to be carried to
the nest and kills the queen ant.
Very effctive they say.

'Terro Ant Killer III" is the full name. It works wonders. I am pretty
sure that it is just a mixture of corn syrup and boric acid, but when I made
my own I did not get rid of the ants. With Terro they are gone.