Boi-tatá () is the Brazilian equivalent of the will-o'-the-wisp. Regionally it is called "Boitatá", "Baitatá", "Batatá", "Bitatá", "Batatão", "Biatatá", "M'boiguaçu", "Mboitatá" and "Mbaê-Tata". The name comes from the Old Tupi language and means "fiery serpent" ("mboî tatá"). Its great fiery eyes leave it almost blind by day, but by night, it can see everything. According to legend, Boi-tatá was a big serpent which survived a great deluge. A "boiguaçu" (a cave anaconda) left its cave after the deluge and, in the dark, went through the fields preying on the animals and corpses, eating exclusively its favorite morsel, the eyes. The collected light from the eaten eyes gave "Boitatá" its fiery gaze. Not really a dragon but a giant snake (in the native language, "boa" or "mboi" or "mboa").