In Greek mythology, the daughter of the river god Argos. Io drew Hera's jealousy when Zeus fell in love with her. Zeus changed her into a white heifer to protect her. Hera sent the many-eyed creature Argus to watch over the heifer, but Zeus sent Hermes to lull Argus to sleep and kill him. Hera then sent a gadfly to pursue Io, who fled across Europe and crossed the bodies of water later named the Ionian Sea and the Bosporus (Ford of the Cow) in her honour. When she arrived in Egypt she resumed her original form. She was later identified with the Egyptian goddess Isis.