About 3 or 4 weeks ago this ant problem was talked about in a thread. Several people mentioned going to Publix and buying Protexall Ant-Kil for about $4 a bottle.
We had this problem, very small ants showing up in our master bath. They were always just outside the shower, so I thought they were coming up through the drain. I sprayed my regular bug killer and the ants kept appearing. I went to Publix and bought Ant-Kil.
It's a tiny bottle. I put just a small amount in two spots near the shower entrance. Within a couple of hours about 30 tiny ants were found dead next to the liquid. A couple of hours later all the ants had evaporated. I haven't put any new amount down and my wife just said there were a few small dead ants next to the liquid. So 3 weeks later it's still working. The liquid is a light blue color so you can see it. However, I wouldn't put it down if you have any pets.