From Wikipedia:
The amphisbaena is a mythological, ant-eating serpent with a head at each end. The creature is alternatively called the amphisbaina, amphisbene, amphisboena, amphisbona, amphista, amfivena, amphivena, or anphivena (the last two being feminine), and is also known as the "Mother of Ants". Its name comes from the Greek words amphis, meaning "both ways", and bainein, meaning "to go".