I am sure that there are people here who know a lot more about the pesky little critters than I do... I think it is weird how there will be several crawling around on you unnoticed and then they all sting at the same time which causes confusion about what is going on.
I had to pull regular fire ant duty to keep them out of the yard in Mississippi. Once I spotted a mound, I filled a 2 1/2 gallon bucket up with water and set in on the stove. Once it was boiling, I carried it out to the mound. Fire ants will swarm out of the ground at the least provocation.
Boiling water always worked. And the dead grass in the cooked spots didn’t have to be mowed.
I read (I think in one of Peter Capstick’s books) about ants in Africa which will gather in their hundreds on a sleeping person and upon a pheromone signal, all bite/sting at once. The assault puts the victim into shock and the ants feed at their leisure. He related a tale of a woman who placed her baby under a tree while she foraged. When she returned the child had been reduced to nearly a skeleton. Ugghh!