Source Verification: Argus Panoptes

Why was Argus considered such an effective guard?

His many eyes did not all close at once - some stayed open and watchful even while others slept, so he was never fully unconscious the way an ordinary guard would be. Hera relied on exactly this quality when she chose him to watch over Io, expecting that no rescue attempt could slip past a watchman who could never be caught entirely off guard.

Source: Ovid, Metamorphoses 1.567-712

How many eyes did Argus actually have?

Sources disagree. Ovid's fuller narrative settles on a hundred eyes, spaced so that some always stayed open while others slept in turn. Aeschylus, in Prometheus Bound, calls him simply "myriad-eyed" without giving an exact figure, treating his watchfulness as effectively countless rather than fixed at a specific number.

Source: Ovid, Metamorphoses 1.567-712; Aeschylus, Prometheus Bound 566-567

Why did Hera want Io guarded in the first place?

Zeus had fallen for Io and turned her into a white heifer to hide the affair from his wife. Hera saw through the disguise but could not openly accuse Zeus, so she asked for the heifer as an innocent-seeming gift, a request he could not refuse without admitting guilt, and then set Argus to guard her once she had possession of the transformed girl.

Source: Apollodorus, Library 2.1.3

How did Hermes get past a guard who was always at least partly awake?

Zeus sent Hermes disguised as an ordinary herdsman to approach Argus without suspicion. Hermes played music and told a long, deliberately tedious story - according to Ovid, the tale of the nymph Syrinx being transformed into reed-pipes - patiently continuing until every one of Argus's many eyes had finally closed in sleep, one after another rather than all at once.

Source: Ovid, Metamorphoses 1.668-721

How did Argus die?

Once none of his eyes remained open to see the blow coming, Hermes killed him, most accounts saying by beheading him with a curved blade. Freed of her guard, Io was able to continue her wandering, though she remained transformed into a heifer for some time afterward before finally being restored to human form in Egypt.

Source: Ovid, Metamorphoses 1.668-721

Why does the peacock have eye-shaped markings on its tail?

After Argus died, Hera gathered his many eyes and set them into the tail feathers of the peacock, her sacred bird, turning her loyal servant's death into a permanent memorial. The eye-shaped markings peacocks are known for today are explained in myth as literally being Argus's own eyes, preserved rather than lost.

Source: Ovid, Metamorphoses 1.720-723

• Ovid, Metamorphoses 1.567-712
• Apollodorus, Library 2.1.3
• Aeschylus, Prometheus Bound 566-567