Procne killed her son by Tereus, Itys (or Itylos), boiled him and served him as a meal to her husband. After he had finished his meal, the sisters presented Tereus with the severed head of his son, and he realised what had been done. He snatched up an axe and pursued them with the intent to kill the sisters. They fled but were almost overtaken by Tereus. In desperation, they prayed to the gods to be turned into birds and escape Tereus' rage and vengeance. The gods transformed Procne into a swallow and Philomela into a nightingale. The swallow generaProgne, Ptyonoprogne and Psalidoprocne derive their names from the myth.
^Salisbury, Joyce E. (2001). Encyclopedia of Women in the Ancient World. ABC-CLIO Ltd. ISBN1576070921.
^ abcdOvid. Metamorphoses Book VI, lines 424–674. (*Note that the line numbers vary among translations).
^Pseudo-Apollodorus, Bibliotheca, 3.14.8; in Frazer, Sir James George (translator/editor). Apollodorus, Library in 2 volumes (Cambridge, Massachusetts: Harvard University Press; London: William Heinemann, Ltd., 1921). (found online  - Retrieved 23 November 2012).