Bald and red patches on cats are often caused by external parasites, infections, or allergies. There may well be something in your damp basement or even in the spray that you’re using that has stimulated the problem in your cat. It's possible that there's more than one cause of the problem or that one factor is the cause and another is making the problem worse. I doubt that one of these factors is the formic acid from the ants, however. You should take your pet to a vet for a diagnosis and treatment. They will be able to identify the cause of your cat's symptoms.