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The only way to solve the problem is to eliminate the nest, and that could be anywhere. If your seeing them in the house at this time of year, chances are there nesting in the house. Check attic perimeters and along basement sills. it can be as easy as the ants living above the vapor barrier of the insulation. Take a walk around the exterior this weekend when it's warm and try to follow them into the house and you'll have any idea of what side to concentrate on. BTW baits don't generally work, but you could try Terro. It has worked for us.