Wayne Boatwright wrote:

I had read somewhere that one could make a solution of water, sugar, and
borax (boric acid?), which was an effective poison for ants. The problem
is that I don't know the proportions that should be used.

Wikipedia (http://en.wikipedia.org/wiki/Boric_acid)
suggests this recipe:

1 tsp boric acid (powder);
10 tsp sugar;
2 cups water.

It works for me.

Good luck