If, as seems likely from what you write, the previous owners knew or under the circumstances, reasonably must have known--i.e. there's no reasonable way someone in their position would not know about the ants but didn't disclose them to you, they may have committed fraud. If so, you may be able to recover compensation, such as the cost of repairs and/or comprehensive extermination. d on what you write, it would be worth your while to consult with a litigator attorney who handles lawsuits about the situation, to evaluate in detail whether under the facts of this situation you have a case, what it might be worth, and what it might cost to pursue it you can then make an informed decision as to whether to file a lawsuit or not.