THE LADONIDES were the Naiad Nymphs of the Arcadian River Ladon (in southern Greece). They transformed their sister Syrinx into a stand of marsh reeds to escape the god Pan.

"The Nympha [Syrinx] fled [from the amorous pursuit of Pan] through the wilderness and came at last to Ladon’s peaceful sandy stream, and there, her flight barred by the river, begged her Sorores Liquidae (Watery Sisters) to change her; and, when Pan thought he had captured her, he held instead only the tall marsh reeds." - Ovid, Metamorphoses 1.689

Sources:

• Ovid, Metamorphoses - Latin Epic C1st BC - C1st AD