The best way to get rid of ants is to target the source.
Individual ants are pretty fragile though. I work in an entomology lab where we do efficacy studies on baits, sprays, etc. for controlling insects. In most of our studies, if we even spray our control (untreated) ants with water, it will significantly increase the mortality almost up to 100%. With that knowledge, almost anything will kill an ant when directly applied. We've worked with D.E. as well and it also works well at killing ants. However, an ant colony is composed of more than just the ants that have come into the house. Killing the ants in the house will only kill a small percentage of the colony and they will just return at a later time or through a different entry point.
The best method I've found is using Terro ant baits. It is a borax-based bait and is supposed to be non-toxic to animals... not that you would willingly offer it to an animal. I would still keep it away from all animals. The worker ants consume the bait and return to the nest to feed the larvae and queen. Once the queen dies, there are no more ants being produced and the colony will die off.
My concern on the bait thing is I have a dog in my house that i am concerned could possibly eat the bait? i dont think he would mess with it if it didn't smell appealing to him but i can't be positive about it.
My chins are very closely watched when they are out so I guess I could just pick up the bait (if possible) while they were out as long as there were no toxic fumes or anything.
Click the link I gave on the first page and it has a picture. It is just a plastic tray that you can easily pick up. I always had the ants on the countertops, so I put the traps there. So I don't know if your dog would be attreacted to them or not. No toxic fumes it is like a syrup, and is supposed to be non-toxic.
It is:
http://www.terro.com/products.php?product=liquid_ant_killer
"The active ingredient, Borax, is recognized by the EPA as being among the safest and least toxic chemicals available to consumers. (One 1 oz drop bottle)"
The tray is under liquid ant baits
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