In Greek mythology, Itylus, or Itylos, was the son of Aedon, daughter of Pandareus of Ephesus and wife of King Zethus of Thebes. Envious of Niobe, the wife of her husband's brother Amphion, who had six sons and six daughters, she formed the plan of killing the eldest of Niobe's sons, but by mistake slew her own son Itylus. Zeus relieved her grief by changing her into a nightingale, whose melancholy tunes are represented by the poet as Aëdon's lamentations about her child. The mythic theme was an ancient one, for Homer's listeners were expected to know the allusion, when Penelope reveals to the still- disguised Odysseus her anguish of a night:
"I lie on my bed, and the sharp anxieties swarming
thick and fast on my beating heart torment my sorrowing self.
As when Pandareos' daughter, the greenwood nightingale
perching in the deep of the forest foliage sings out
her lovely sing when springtime is just begun, she varying
the manifold strains of her voice, pours out the melody
mourning Itylos, son of the lord Zethos, her own beloved
child, whom she once killed with the bronze, when the madness was upon her;
As one of only nine similes in the Odyssey that are longer than five lines, the thematic complexity of the image and its multiple points of contact with Penelope's situation has arrested the attention of many readers. Aedon accidentally killed Itylus "in her madness" and was stricken with grief and guilt. In pity, the gods turned her into a nightingale, which cries with sadness every night. In an explanatory scholium on this passage, an anonymous scholiast, echoed by Eustathius, explains that Aedon attempted to kill the son of her sister-in-law and rival, Niobe, but accidentally killed her own son instead: thus, the gods changed her into a nightingale to weep for eternity. The setting of the episode is Thebes.
Attic authors later than Homer, including the dramatists knew a nightingale myth in which Procne was married to Tereus, who betrayed her by violating her sister Philomela, whose tongue he cut out so that she could not tell. (In some versions, Philomela is the name of the wife, Procne of her mutilated sister.) Philomela wove her story into a robe that she gave to Procne. In a fit of madness Procne murdered her own child by Tereus, Itys. All were changed to birds, the murderous mother to a nightingale.