An ant death spiral, also known as an ant mill, occurs when ants get separated from the rest of the foraging party and end up following the scent of the ants in front of them in an endless loop. Eventually, the ants became exhausted and perish.
Ants cannot see, so they rely on pheromones for navigation. Because they instinctively follow the ants in front of them, one separated ant can lead others astray. If the leader of the group eventually loops behind another ant, the result is a continuing spiral with no forward direction. Unless their path is interrupted, they do not stray from the odor in front of them.