These non- flying ants might not mate with the flying ants, and so they would be considered to be a new species. Quite the opposite. This hypothetical new species of ant is a step backwards, not forwards. It has lost the ability to fly because it has lost a required gene. This junk DNA no longer serves any purpose.
Devolution is consistent with the second law of thermodynamics.
Given enough time, and left to themselves, things fall apart. Things don't naturally fall together. So it is possible that flying ants could devolve into ordinary ants because one of the genes needed for flying could be lost or damaged. For flight-challenged ants to evolve into flying ants, at least one new gene would have to be added. There is no evidence that this happens now, or has ever happened in the past.