http://www.mythweb.com/encyc/entries/ladon.html
A many-headed dragon who watched over the garden of the Hesperides. When Heracles as one of his Labors sought the golden apples in the keeping of these Daughters of the Evening, he had to enlist the aid of the Titan Atlas. Atlas was willing to steal the apples if Heracles relieved him of his burden of holding up the heavens, but only if the hero first did something about Ladon. Heracles killed the dragon with an arrow over the garden wall.