If you have access to an animal feed store - (grain elevator) that sells dried molasses (horse feed supplement, used to sweeten horse feed and add flavor), it works great against ants. Wet molasses will not work. It has to be dried.
Put some in a soft drink plastic cap, or a plastic milk bottle cap and put leave out anywhere you see ants.
Here's how it works. The ants come in, they take the molasses granuals back to their nest, they consume it (as does the queen). Because ants are hard shelled and their shells do not expand, once the molasses is consumed, it expands (because it gets wet), and the ants explode! Dead! There goes the queen! There goes the nest!
Outside: Just sprinkle on the ground around your house, camper, whatever, like you're spreading chicken feed or grass seed. The ants will find it, take it back to their nests, and the rest is history.
Ant hill? Sprinkle a generous handfull on the top of the hill. 2 days later, you wont' have any ants at that hill.
And here's the benefits. It will not hurt birds, raccoons, pets, mice, or anything else. Is safe for human consumption (I've eaten my share of it when demonstrating to people it's safe), and it smells really nice!
My wife discovered this bit of information from Bird Talk Magazine several years ago when we had birds and ants, and using chemicals to kill the ants were just out of the question because the fumes would hurt the birds. The article also said you'll never see ants on a farm where they feed horses if they've been using the molasses. So I checked with a couple horse farmers I know and sure enough, they never equated the molasses with lack of ants around their feeding stations.
So we've been using this for some ... 20 years now, in 2 different houses. I just bought a bag last Monday (again), to share with my neighbor. He's having a bad ant problem at home. I'm not having any problems. We live in the country, so I'm waiting for this round of rain to end and will sprinkle both yards and around his house (probably this week-end).
I take a small bucket (with a lid) with us when we go camping and the first thing I usually do is sprinkle it around the camper on the ground. No need to put it inside.
There are 4 down-sides to using the dried molasses. 1) it comes in 50 pound bags. 2) it dries hard and crusty on the exposed surface if you don't keep it sealed tight. 3) its hard to find if you don't live in a farming community 4) it's deadly to any ant that values his life!
Others swear to Ortho, or some of those types of chemicals. And yes, they do work, but they are also poison to everything else that breathes also!