According to Greek mythology the sirens were born to three drops of blood of Achelous, god of rivers, wounded in battle by Heracles. Once generated they settled on some islands of the Tyrrhenian Sea off the coast of Naples.
were also called Nereids, because according to a senior myth, were believed to be daughters of the sea god Nereus and Doris.
As the Harpies and Furies belonged to the gods of the dead could also be benign.
They were not represented today as we imagine them: they were fabulous creatures from the bird's body and the head of a woman!
So very different from the famous Little Mermaid of Hans Christian Andersen's fairy tales, which had in common, however, the seductive song that attracted the sailors who passed near their islands.
In an episode of the Odyssey, Odysseus return to Ithaca, is beyond the point of making their tie to the mast of his ship, after having plugged the ears of his sailors with wax.
In this myth sirens defeated by Ulysses decided to commit suicide by jumping into the sea, a dead bird can then only to women and certainly not to creatures that were half-fish.
What had feathers and wings of a bird or fish-tail point of the speech remains the same: they were lured to the men who would lead inexorably to ruin.
bewitched not only by the sensuality of their singing, but also with their beauty and their nakedness. Especially for the fact that a union with them could not in any case lead to the conception of children, that was perhaps the most negative of their being.
For the ancient Greeks it was considered a great misfortune not to produce children and can not therefore give rise to its own breed.
In later times their myth change: from absolute representation of the curse of perdition and are in a sense "revalued" become the compassionate companions for the deceased in the afterlife
are still represented as winged beings since, in different cultures, death is represented as soul flight.
How is it then that today we stand for as human half-fish?
The "fault" is probably of Christianity is again given them a negative meaning, of destruction, so could not be represented with wings, typical physical characteristic of the angels. 
Their spread, however, is global: it is known in almost all cultures and there are many statues (Copenhagen) and paintings that represent them. Their description will be even in the medieval bestiary (which at the time had scientific value as our current encyclopedias), and then considered living beings and not myths! Being so
represented in the whole world, is almost wonder if they actually are mythological beings or whether they ever really existed!
In 1842 it was exhibited by a specimen of the Barnum Circus siren then proved a resounding false, obtained by joining the remains of a monkey with a fish.
Unfortunately, the nature reserve even more striking surprises: the mermaid syndrome (a combination of the lower extremities) hits a baby every 70 000, and forces to delicate surgery.
Mythical charmer, winged escort anime mermaids their romantic myth is constantly evolving: it is because of this that even today their myth is still present.
