Diatomaceous earth is cheap, non-toxic, and will kill any bugs that get into contact with it. Ants, spiders, etc. It's like microscopic razor blades that get into their joints like sand in gears, and tears them up. It stops working when it gets wet, so it's not bad for humans and pets. My cat sometimes rolls in the stuff, and I was worried about it getting in his eyes and nose, but he's fine.
