The Harpies, who, like the Furies, were employed by the gods as instruments for the punishment of the guilty, were three female divinities, daughters of Thaumas and Electra, called Aello, Ocypete, and Celæno.
They were represented with the head of a fair-haired maiden and the body of a vulture, and were perpetually devoured by the pangs of insatiable hunger, which caused them to torment their victims by robbing them of their food; this they either devoured with great gluttony, or defiled in such a manner as to render it unfit to be eaten.
Their wonderfully rapid flight far surpassed that of birds, or even of the winds themselves. If any mortal suddenly and unaccountably disappeared, the Harpies were believed to have carried him off. Thus they were supposed to have borne away the daughters of King Pandareos to act as servants to the Erinyes.
The Harpies would appear to be personifications of sudden tempests, which, with ruthless violence, sweep over whole districts, carrying off or injuring all before them.
From: Berens, E.M. The Myths and Legends of Ancient Greece and Rome. New York: Maynard, Merril, & Co., 1880. Text in the public domain.