I had an old rotten tree stump in backyard that was crumbling apart and and the ground was caving in where roots ran. So decided it was time to dig it up. To my surprise, the entire stump and root system was a massive fire ant colony. No mounds around to warn me so first shovel into ground brought on a fierce attack and I got bit at least 20 times in seconds.
I demolished the stump with just a few hits of shovel and dug up large hollow root sections that had been part of colony. Had to quit because ants were crawling up water hose, shovel and up my legs and arms fazter than I could spray them off. I am going to treat entire yard with bait and then area were most of colony still lives. Not up to fighting fire ants like that. Once I think the colony is dead, I will finish digging up the hollow roots.