I compare fire ants to yellow jackets. A wasp sting hurts and goes away, a yellow jacket sting stays with out. To a lesser degree so do fire ant stings or bites, they tend to burn for much longer than a regular red ant. Frequently because of the density of them you will find yourself with multiple bites. I have never seen a fire ant mound as small as a red ant mound and vice verse. Down here the first time you notice a fire ant mound it will be at least 3 - 4 inches above the surround surface and seem to appear overnight. I think Jim mentioned them forming rafts and floating away during flooding. I remember a photo of where a bream had been killed supposedly by the ants and they were floating and feasting on it during flooding.