Reading the French version of Journey to the Ants by Bert Hölldobler and Edward O. Wilson (1996) during the course of my graduate studies, I remember being amazed by the description of circular mills formed by an isolated group of army ants. This phenomenon occurs when a group of foragers is separated from the main column of the raiding swarm by a perturbation of their pheromonal communication (Schneirla 1944). The separated workers then run in a densely packed circle until they all die from exhaustion (Schneirla 1971)…
This natural phenomenon is reproducible in the laboratory and has recently been shown to result from a self-organizing pattern (Couzin and Franks 2003). After a period of disorder, a random direction is collectively selected by ants, and a circular mill forms, following simple rules of motion governed by direct interactions between individuals.
Here's a video of what that looks like:
How's that for a metaphor of what happened during Reddit's "hunt for the Boston bombers"? Thousands of users, cut off from any objective measure of whether they're right or wrong, just following each other in circles until they die from exhaustion. Except that in this metaphor, it's not the ants who are hurt, but their target.