Ant mill
An ant mill is a small group of army ants away from the other ants. They lose the pheromone track and begin to follow each other, making a spinning circle. This circle is also known as a "death spiral" because the ants will eventually die of exhaustion.  People can make this happen easily.  This is a side effect of the self organizing structure of ant colonies. Each ant only knows to follow the ant in front of it. This will work until something goes wrong and an ant mill forms.  An ant mill was first seen by William Beebe who saw a mill 1,200 feet in circumference.  It took each ant 2.5 hours to go around.