The constellation, which had originally formed part of the claws of the scorpion (Scorpio), is the youngest of the Zodiac and the only one not to represent a living creature. In later Greek mythology, the constellation, which when considered on its own looks vaguely like a set of scales, was considered to depict the scales held by Astraea (identified as Virgo), the goddess of justice.

Since Libra was originally part of Virgo (as scales), and before that part of Scorpio, it was not a distinct entity for which a zodiac sign was named. Its place may have been taken by Bo��, which is the nearest to the ecliptic. Since the place Bo�� should have held on the ecliptic is vacant, it may have, together with Ursa Major, Draco, and Ursa Minor, also in Libra, led to the myth of the apples of the Hesperides, one of The Twelve Labours of Herakles