Desert ants travel long distances to find food, using celestial cues to orient themselves and find their way. Scientists knew the ants must also have a method for determining exactly how far they have marched, but until now they were uncertain of the mechanism. A new experiment has revealed that the ants measure distance with some sort of internal pedometer, based on stride length. Researchers altered the legs of a group of ants, giving some "stilts," like the Cataglyphis ant shown above with red leg extensions. Other ants received "stumps," their legs shortened by amputation. The ants on stilts had a lengthened stride and marched past their goal, whereas the stump-legged ants stopped short of their goal, suggesting that stride length indeed serves as an ant pedometer. The research is detailed in the current issue of Science.