In Greek mythology, daughter of Inachus, a river God. She was a virgin (chaste) priestess of Hera, who earned Hera"s wrath by attracting the attention of Zeus. According to Aeschylus (in his Prometheus Bound), Io was exiled and turned into a cow (by either Zeus or Hera) and was stung continually by gadflies (sent by Hera) in order to stop from her from resting anywhere long enough for Zeus to unite with her. Argus, a giant with a hundred unsleeping eyes, was charged by Hera to guard over her for the same purpose. The giant was killed by Hermes (Mercury). She was pursued by the flies and wandered all over until finally arriving in Egypt where Zeus changed her back into a woman and, with a touch of his hand, impregnated her. This is but one of several versions of her story; Ovid in his Metamorphasis tells another. Io came to be worshipped as the goddess Isis and had a son named Epaphus who was worshipped as the bull-deity Apis.