The Amphivena is a mythological, ant-eating serpent with a head at each end. According to Greek mythology, the Amphivena was spawned from the blood that dripped from the Gorgon Medusa's head as Perseus flew over the Libyan Desert with it in his hand. Cato's army then encountered it along with other serpents on the march. Amphivena fed off of the corpses left behind.
(Source: Wikipedia)