Argos (or Argus) was a Greek hero, who had only one eye (another
version gives him four eyes, yet another one gives him many eyes). He fulfilled
many labors: freed Arcadia from a gigantic bull, killed Satyr, who harmed
Arcadians, slew Echidna, the monstrous daughter of Tartarus. Hera
employed him to watch over the white heifer Io,
of whom she was jealous. Thanks to his many eyes he could watch Io day
and night. Zeus asked Hermes
(Mercury) for help. Having put Argos to sleep by magic, Hermes slew him.
Willing to give immortality to her faithful servant, Hera moved his many
eyes to the tail of peacock, sacred bird of Argos.
See: Peter Paul Rubens Argus
and Mercury.
Diego Velázquez. Mercury
and Argus.