cow could eat, thus growing "from her from whom it has its name", based on incorrect folk etymology. The various colours of the violet (red, purple, white) changed on account of Io's life, red for the blushing maiden, purple for the cow, white for the stars. Hera then sent Argus Panoptes, a giant who had 100 eyes, to watch Io and prevent Zeus from visiting her, and so Zeus sent Hermes to distract and eventually slay Argus. According to Ovid, he did so by first lulling him to sleep by playing the panpipes and telling stories. Zeus freed Io, still in the form of a heifer. In some myths, Hera uses Argus' eyes to decorate her peacock's feathers to thank the giant for his help. In order to exact her revenge, Hera sent a gadfly to sting Io continuously, driving her to wander the world without rest. Io eventually crossed the path between the Propontis and the Black Sea, which thus acquired the name Bosporus (meaning ox passage), where she met Prometheus, who had been chained on Mt. Caucasus by Zeus. Prometheus comforted Io with the information that she would be restored to human form and become the ancestress of the greatest of all heroes, Heracles (Hercules). Io escaped across the Ionian Sea to Egypt, where she was restored to human form by Zeus. There, she gave birth to Zeus's son Epaphus, and a daughter as well, Keroessa. She later married Egyptian king Telegonus. Their grandson, Danaus, eventually returned to Greece with his fifty daughters (the Danaids), as recalled in Aeschylus' play The Suppliants. The myth of Io must have been well known to Homer, who often calls Hermes Argeiphontes, which is often translated as "Argus-slayer", though this interpretation is disputed by Robert Beekes. Walter Burkert notes that the story of Io was told in the ancient epic tradition at least four times of which we have traces: in the Danais, in the Phoronis—Phoroneus founded the cult of Hera, according to Hyginus' Fabulae 274 and 143—in a fragment of the Hesiodic Aigimios, as well as in similarly fragmentary Hesiodic Catalogue of Women. A mourning commemoration of Io was observed at the Heraion of Argos into classical times. The ancients connected Io with the Moon, and in Aeschylus' Prometheus Bound, where Io encounters Prometheus, she refers to herself as "the horned virgin". From her relationship with Phoroneus, as sister (or descendant),