When we moved into our new (to us) home a few years ago we inherited a severe ant problem. There were at least four varieties from almost too small to see to quarter inch monsters.
We tried all the tricks from insecticides to boric acid to no avail.
Then a nest of ground termites moved into the neighbors yard and we decided it was time to call in the professionals. They got rid of the termites, with the added benefit of no more ants. It costs about fifty bucks a month but it's well worth it for the termites alone.