In Greek mythology, an amphisbaena was an ant-eating, two-headed serpent. The strangest thing about an amphisbaena is that one of its two heads is at the end of its tail.
You'll come across an amphisbaena in any good collection of Greek myths — sometimes it's called the "Mother of Ants." The stories about the amphisbaena are all fairly bloody, as it was born from a drop of blood that fell from Medusa's severed head and proceeded to feed not just on ants, but also on various dead bodies. The word amphisbaena combines two Greek roots, amphis, "both ways," and bainein, "to go."