Hunched over a treadmill designed for arthropods, biologist Robert Full tests an Arizona centipede in his laboratory at UC Berkeley (California). Even though the centipede has forty legs, it runs much like an ordinary six-legged insect. Just as insects move on two alternating sets of three legs (two on one side, one on the other), the centipede gathers its legs into three alternating groups, with the tips of the feet in each group bunched together. From the book Robo sapiens: Evolution of a New Species, page 94 top.