Fire ants produce an alarm pheromone that may be released by a worker if it recognizes another ant as a non-nestmate, or by some disturbance. When the alarm pheromone is detected by a nestmate the detecting ant moves rapidly in what appears to be an erratic pattern toward the the alarm pheromone source until it encounters another stimulus, after which it may release alarm pheromone and sting. A person may unknowingly stand where fire ant workers are active and the ants may crawl up that person’s leg. Many undisturbed workers may wind up on the person’s leg before the person senses something on their leg. The resulting scratching or movement induces one or more ants to release alarm pheromone and sting. The alarm pheromone is very volatile and acts quickly on the other nearby ants, so that it seems as though they are stinging all at the same time.