If you've never seen a fire ant bed, here's a view.
According to Texas A&M, one should KEEP the native Texas fire ants since they fight against the imported fire ants from Argentina. To tell them apart, you simply look closely at their mandibles. Uhh...okay..
If the fire ant has 3 protrusions on the mandible, leave it alone. It's a good guy.
If it has 4, it's the bad guy. As you can see by the above picture, it will take a platform stereoscope to see this difference. ( I have access to one..don't we all?!)