take your mortar and pestle, and grind together 1tsp of dry yeast, and 1 tspn white sugar into a fine powder...mix into 1tspn honey, to make a paste.
Place drops (around 1/2") onto some flat al foil where they will definitely come across it.
You'll have heaps of ants come in to get the sugar yeast mixture, wander away, and it will start to ferment, killing them, but back in their hole.