SEMELE, a beautiful princess, the daughter of Cadmus, king of Phoenicia, was greatly beloved by Zeus.
Like the unfortunate Callisto, she was hated by Hera with jealous malignity, and the haughty queen of heaven determined to effect her destruction. Disguising herself, therefore, as Beroe, Semele's faithful old nurse, she artfully persuaded her to insist upon Zeus visiting her, as he appeared to Hera, in all his power and glory, well knowing that this would cause her instant death. Semele, suspecting no treachery, followed the advice of her supposed nurse; and the next time Zeus came to her, she earnestly entreated him to grant the favour she was about to ask.
Zeus swore by the Styx (which was to the gods an irrevocable oath) to accede to her request whatsoever it might be. Semele, therefore, secure of gaining her petition, begged of Zeus to appear to her in all the glory of his divine power and majesty. As he had sworn to grant whatever she asked of him, he was compelled to comply with her wish; he therefore revealed himself as the mighty lord of the universe, accompanied by thunder and lightning, and she was instantly consumed in the flames. Io, daughter of Inachus, king of Argos, was a priestess of Hera. She was very beautiful, and Zeus, who was much attached to her, transformed her into a white cow, in order to defeat the jealous intrigues of Hera, who, however, was not to be deceived.
Aware of the stratagem, she contrived to obtain the animal from Zeus, and placed her under the watchful care of a man called Argus-Panoptes, who fastened her to an olive-tree in the grove of Hera. He had a hundred eyes, of which, when asleep, he never closed more than two at a time; being thus always on the watch, Hera found him extremely useful in keeping guard over Io. Hermes, however, by the command of Zeus, succeeded in putting all his eyes to sleep with the sound of his magic lyre, and then, taking advantage of his helpless condition, slew him.
The story goes, that in commemoration of the services which Argus had rendered her, Hera placed his eyes on the tail of a peacock, as a lasting memorial of her gratitude. Ever fertile in resource, Hera now sent a gadfly to worry and torment the unfortunate Io incessantly, and she wandered all over the world in hopes of escaping from her tormentor.
At length she reached Egypt, where she found rest and freedom from the persecutions of her enemy. On the banks of the Nile she resumed her original form and gave birth to a son called Epaphus, who afterwards became king of Egypt, and built the famous city of Memphis.
From: Berens, E.M. The Myths and Legends of Ancient Greece and Rome. New York: Maynard, Merril, & Co., 1880. Text in the public domain.