The basement of my house and backyard are home to numerous colonies of Argentine ants, a species of small ants that is enormously successful in California (their colonies have multiple queens and their diet is especially flexible). Now and then they decide to relocate into my kitchen, using cracks and pinholes as their points of entry.
To be sure, Argentine ants are a lot less trouble than the fire ants of the Southwest, but because they are so relentless and numerous — scouts always looking for new sources of food or new places to set up a colony, a speck of food or few drops of water triggering hundreds to rush in — it can be a frustrating battle.
Some time ago, my upstairs neighbor gave me one of those “green tips” that we see everywhere. The tip suggested that peppermint oil (or probably essential oil from chili, cinnamon, spearmint, or wintergreen) could be an ant deterrent. The peppermint oil interferes with their senses and obscures the chemical trails that ants leave behind. (here is an interesting story about how ants use chemical signals to decide whether they should go looking for food, and a fascinating radio program from WNYC’s Radiolab that includes some notes about how ants behave)
To apply it in the war against ants, I put a few drops on a cotton swab and wipe the oil along the ants’ entry points into the house. I usually need to reapply it every few days until the ants stop coming inside.
Peppermint oil only works, however, if you can figure out where the ants are entering the house. If they are coming through a crack in the back of your deepest cupboard or underneath your refrigerator, you’ll have trouble applying the oil in the right place. But since the oil is non-toxic, not too expensive, and leaves a strong peppermint aroma in the air, it might be worth trying to swab it where you see ants.
So until there is something better, like a commercially available naturally-occuring chemical that causes ants to attack each other, I’ll keep swabbing the peppermint oil.