Last year I had a trail of ants along a path and couldn't find a nest but I've found borax and sugar work well (they take it back to the nest). The trouble is finding something that you can put it in that a dog or cat can't get into. Fruit containers work perfectly because you can close them and they have small holes in the bottom for the ants to crawl in. Wait until you get it into place before adding the borax and confectioners sugar (mix in equal parts) to avoid the mixture from spilling through the holes before you put it in place.
