I keep a decently clean kitchen. I regularly sweep, mop, and scrub the counters and sink. Once in a while I'll leave a half-rinsed pan in the sink, but I always wash everything before going to bed. The only things that are left out are whatever is in my fruit basket and a serving of cat kibble.
Ants got in and found the kibble. When I cleaned up that and poured salt in the crack they were coming through, they found another way in. And another, and another, and another. I left the bottle of shower bleach on the counter all week, zapping every stray that dared to invade. I must have gone through a cup of salt.
Then I finally thought to ask others what they do. One woman on the cryptograms site forwarded a link to a child- and pet-safe site of ant fighting remedies. I was shocked and dismayed to find out that Aspartame is a pesticide. Fortunately, I keep artificial sweeteners for guests and opened a packet all over the counter, tossed a handful of cornmeal over it, and figured I'd clean up everything after shopping for a more permanent solution.
20-mule team site in Death Valley. Cousin Smurf uses it to freshen her laundry because she's allergic to perfumes and dyes. Apparently, it's also a pesticide that works on the smallest of household intruders: ants, fleas, some roaches, silverfish, spiders, and pretty much anything that weighs less than a dime.
I didn't do the sugar caps outside because of the cats and all kinds of critters in the neighborhood. I bought sealed outdoor-grade ant traps to attack the colonies. But I did scrub the whole kitchen and reline the spice cabinet (had to throw out a couple of containers because the contents were moving), allowing some borax residue to remain in the cracks. A spider crawled across the wet floor and promptly died, so I must have done it right.
It's too early to know if the choice of cleaning product made as much of a difference as loosing the wrath of ant baits did. (The commercial Terro baits are borax-based.) The sprinklers also ran the day they stopped coming in, so maybe they were just looking for water and I only run the sprinklers once a week. I still haven't put the cat food back on the floor. They're eating on the dining room table. I know, posh cats.