Ant odometer

Ants are social insects that evolved from vespoid wasps in the mid-Cretaceous period, about 150 million years ago. After the rise of flowering plants, about 100 million years ago, ants diversified into numerous species. The Sahara desert ant travels immense distances over sandy terrain, often completely devoid of landmarks, as it searches for food. These creatures are able to return to their nests using a direct route rather than by retracing their outbound path. Not only they judge directions, using light from the sky for orientation, but they also appear to have a built-in "computer" that functions like a pedometer that counts their steps and allows them to measure exact distances. An ant may travel as far as 160 feet (about 50 meters) until it encounter a dead insect, whereupon it tears a piece to carry directly back to its nest, accessed via a hole often less than a millimeter in diameter. By manipulating the leg lengths of ants to give them longer and shorter strides, a research team of German and Swiss scientists discovered that ants "count" steps to judge distance. For example, after ants had reached their destination, the legs were lengthened by adding stilts or shortened by partial amputation. The researchers then returned the ants so that the ants could start on their journey back to the nest. Ants with the stilts traveled too far and passed best entrance, while those with the amputated legs did not reach it. However, if the ants started their journey from their nest with the modified legs, they were able to compute the appropriate distances. This suggests that stride length is the crucial factor. Moreover, the highly sophisticated computer in the ant's brain enables the ant to compute a quantity related to the horizontal projections of its path so that it doesn't not become lost even if the sandy landscape develops hills and valleys during its journey.