Ozark Lady wrote:I have also heard that ants won't cross lines of white flour, white sugar, or orange peels, not sure it is so. And not so sure that I want those on my window sills to keep ants out either.
IMO, the ants would be drawn to those substances. What does work, though, is ordinary white chalk. (Actually, any color would work, but colored chalk often leaves stains.) My grandmother used to draw a chalk line around every window and along every exterior door sill in our house every spring. We had ants all over the place outdoors, but nary a one inside the house. (I used to laugh at her chalk lines, but I was a smart-alecky brat of a kid.
The trick is that the line can't have any breaks in it, and it has to be wider than the ant is long. The reason it works is that they breathe through openings on their abdomen. Any kind of fine, dusty stuff can clog the openings and suffocate them.
So, in desperation, I used chalk myself one year, after Terro, Grant's, and my usual borax mixture didn't have any effect on the invaders. I used French White chalk, which I found in my dog grooming kit ... left over from my Koms. It's softer than blackboard chalk, and was easier for me to put down in a wide, unbroken line. It worked. I found that the ants were entering through a foundation vent under my kitchen window, crawling up through the wall, and exiting onto my kitchen counter from behind a piece of moulding. I drew the chalk line all around the foundation vent. No more ants! I was amazed!