By now, you may know that lemmings don't really commit mass suicide. But did you know that ants sometimes do? In the video above, a few dozen army ants (species Labidus praedator) engage in an creepy ritual entomologists call an "ant mill." Unless something disrupts their spiraling path, they'll keep following it until they die from exhaustion.
explains in a Discovery Channel video. Each follows the odor trail of the ant ahead of it--so if the leader loops around and starts following another ant in the group, a death spiral can result.
Biologist and insect photographer extraordinaire Alex Wild noted on his blog that this sort of behavior can arise from such simple situations as a few ants exploring a coffee cup. But it can also be huge—one spiral, 1200 feet in circumference, was observed by American naturalist William Beebe in Guyana in 1921.
It may seem like an evolutionary glitch, but the fact that ants aren't big on critical thinking actually has some interesting applications. Ants' behavior is generally determined by only a few simple rules, such as "follow the ant in front of you," and this makes them a useful model in some artificial intelligence simulations. These so-called "ant colony optimization" algorithms use ant-like objects to solve problems such as finding the most efficient route through a maze. Since 'bugs' like the ant mill can be a big problem in those simulations, programmers usually add safety measures to keep the ants on track.