I put a Terro liquid ant bait (made of Borax), and the Pharaoh Ants were attracted to it. But as they went inside, they slowly build some kind of sand mount in the entrance. The bait hole is a bit higher up the surface, were they constructing some kinds of steps? Why are their putting dirts even inside the Terro? At first I thought the ants were trying to neutralize the Borax with some kinds of compounds. But they seem to get fewer in numbers so the Borax could be effective.
What kinds of reactions to neutralize Borax anyway?