Ant traps don't work, in my experience. They actually seem to attract the ants into the house. It makes sense. After all, they telegraph when they've found food. It's presumptuous to think they all come from the same ant bed. It also seems to have little to do with how clean you keep things. They just seem drawn to zero in every Spring.

My husband seems to have hit upon a working method to keep them out of the house. When we first saw them, he began doing this. He heavily sprays the perimeter around the outside of the house, around the foundations, with the best ant spray we can afford – no skimping. Then, he takes isopropyl alcohol in a squirt bottle and skirts a steady stream along all the baseboards and backs of counters and cupboards – he is averse to using insecticides in the house because of my health and our dog (who's not always the brightest bulb in the pack). The theory there is that it breaks the food smell drawing them into the house. Then, hubby sprays the perimeter again every month or so. We've had three years without them in the house.