Philomela (ˌfɪləˈmiːlə) or Philomel (ˈfɪləˌmɛl; , ; Φιλομήλα ) is a minor figure in Greek mythology who is frequently invoked as a direct and figurative symbol in literary and artistic works in the Western canon. Philomela was the younger of two daughters of Pandion I, King of Athens, and the naiad Zeuxippe. Her sister, Procne, was the wife of King Tereus of Thrace. Philomela's other siblings were Erechtheus, Butes and possibly Teuthras. While the myth has several variations, the general depiction is that Philomela, after being raped and mutilated by her sister's husband, Tereus, obtains her revenge and is transformed into a nightingale (Luscinia megarhynchos), a bird renowned for its song. Because of the violence associated with the myth, the song of the nightingale is often depicted or interpreted as a sorrowful lament. In nature, the female nightingale is actually mute, and only the male of the species sings. Ovid and other writers have made the association that the etymology of her name was "lover of song", derived from the Greek φιλο- and μέλος ("song") instead of μῆλον ("fruit" or "sheep"), which means "lover of fruit", "lover of apples", or "lover of sheep". The most complete and extant rendering of the story of Philomela, Procne, and Tereus can be found in Book VI of the Metamorphoses of the Roman poet Ovid (Publius Ovidius Naso) (43 BC – 17/18 AD), where the story reaches its full development during antiquity. It is likely that Ovid relied upon Greek and Latin sources that were available in his era such as the Bibliotheca of Pseudo-Apollodorus (2nd century BC), or sources that are no longer extant or exist today only in fragments—especially Sophocles' tragic drama Tereus (5th century BC). According to Ovid, in the fifth year of Procne's marriage to Tereus, King of Thrace and son of Ares, she asked her husband to "Let me at Athens my dear sister see / Or let her come to Thrace, and visit me." Tereus agreed to travel to Athens and escort her sister, Philomela, to Thrace.