This name may refer to this creature. In some places online known as Phagocyte, Genie Ghouls, Axe Ghosts, possibly Flow Werouwous or Eagler (re previous editors names), perhaps other. There may not be an official name, as many of the creatures in the game there is no (known) documented name in a manual and they are not featured in the end credits.
They are found on stages 4 part 1, or 7 (maybe 6 as well.) They don't track the player and they fly in either a horizontal or vertical sine wave pattern.