With some hyperbole, you could say that an ant’s body comprises the World’s Smallest GPS System:
Despite zigzagging across flat, monotonous terrain looking for food, Saharan desert ants always head home via the shortest possible route. Like many insects, the ants use polarized sunlight to get direction, but how do they measure distance? To find out, neurobiologist Harald Wolf of the University of Ulm in Germany caught ants at a feeder 30 feet away from their nest. Some ants’ legs were extended by gluing on pig bristles, while other ants’ legs were severed below the knee. On the return trip, the ants on stilts overshot the nest, while those with severed legs stopped short. Wolf concludes the ants count their steps via an internal pedometer that is part of their nervous system, making them the only creatures known to do so.