My kitchen is under invasion by ants. They've been all over the place for a week now.

I've tried a commercial Borax poison but the ants just eat it up and come back for more.

Any idea on how to get rid of them?

Magnifying glass?

Fire.

They are taking the borax back to the colony. It might be longer than a week before the queen dies.

Keep killing them as much as you can. If you inflict more casualty's than they can replace, they will be forced to move the colony. Or at least that's what I read once. I don't know if its true.

Diatomaceous earth is also a good deterrent.

a)Run to the hills!*

B)More ant traps!
Find the source, we used to have pharaoh ants in the kitchen. And they kept coming, anc coming, until my neighbours, who live on the other side of the wall [twin/row house thingee] started fighting them with the same thing. Didn't take long, really. Key is, to attack all their 'bases'. I'd have to ask mom, what exactly we used, to be sure.

*unless ants are coming from the hills. if they come from all directions, goto b.

Ant Farm!

Blow up the kitchen. Ant problem is solved.

There is a trick to ants, poison works but not all poison will work on the same types of ants. So, for example, the pesky ones in my area are called "small black", if you buy ant bait/poison at Target or Walmart you most likely will grab something intended for other types of ants and they will not die.

If you can identify the ant type and then place ant poison designed for that ant type it will most likely work.

Also, clean shit up, you may think your kitchen is clean but crumbs in the back of a cupboard could screw you. No plates get to sit on the counter overnight or that bit of ketchup will invite an entire colony.

Good luck. My experience is that even potent vinegar will not destroy scent trails sufficiently.

Cinnamon is actually surprisingly effective against ants. They really don't like it. It won't kill the colony, but it'll keep them out of your house. Sprinkle it at all entry points (if you know where they're getting in). Also, sprinkle a bit on every ant you see, and then leave it alone. When it returns to the colony, no other ants will follow its trail (or so I've read).

^^
This. We started doing this a few years ago because those tiny black "sugar ants" (I don't know what they are really called) kept showing up every summer, despite using commercial "insecticide shields". Every spring I sprinkle a generous amount of cinnamon at the doorways and a little bit in each window and no ants ever again. The most amazingly effective folk remedy I've ever seen. Plus it makes the house smell real nice.

How big of an invasion are we talking about? When I was a kid my parents had the house raided by carpenter ants, but we're talking just about every ant in the area. The cause was a drought and they were looking for water.

I recall the way they handled it was with lots of bug spray and then sweeping up the corpses with a broom.

Find the offending anthill, grab a mattock and go to town on it. Once you've dug out the queen's chamber, coat what's left in ant sand. Problem solved.