Borax Ant Killer
1 cup of very warm water
½ cup of sugar
2 tablespoons of borax powder (found in laundry aisle)
Mix the solution until all particles have dissolved. Dunk cotton balls in the solution. Once the cotton ball is saturated, place it on stiff paper on or near all of the trails that you see.
You should see the ants flock to these things like crazy. When the ants come to the cotton balls, the temptation is to kill them - don't! The ants will take their new "food" back to the ant hill where the other ants in the colony feed off of this sugar borax solution. Once the borax gets into the colony, most of the ants will die within 24 hours.
Keep the remaining solution in the refrigerator. You may need to put out some new cotton balls with the solution a few days later. Mix well before every use.
If you follow this process you should be ant free soon. We had probably 10 colonies in our yard and it only took a few reapplications to get rid of most.