Fire ants, commonly found across the southern United States, earn their name from the painful stings they deliver. One way to tell if you have a fiery infestation is to look for a large group of ants that are reddish-brown to reddish-black and measure between 1/8 to 1/3 inch in length. You will also likely notice dome-shaped mounds of soil scattered across your lawn. A key characteristic of these fire ant mounds is that they will not have an exit hole or a visible entry point.