When i went on holiday to Spain we had a barbecue, food all over the floor(?). Next morning ants were marching ALL the way across and 18 Foot room, and then splitting off, it was amazing to watch. I had to kill them though. It was easy, heres how you do it (worked perfectly) soak Pear's Banana and a bit of tuna in water boiled with sugar. Poor the liquid somewhere you can easily access. 20m Minutes later all ants probably a few thousand were all over it.
Now the fun part, i covered the area with a large plastic box, got a ping pong ball put a hole in it and sprayed it with thin bleach spray. Covered it in foil and then heated it up a lot, chucked it under the box and watched. It releases a lot of smoke and creates a quick blast of heat when it gets into the ping pong balls. The bleach smoke stuff seemed to poison them all. They all died in about 5 minutes,
But warning the room had no wall so you walked out into the pool, it was like a very large sheltered room with no wall so you could walk out to the pool. So don't do it in a confined space. I'm sure they was a much easier way to kill them, but that was fun and i read it somewhere.