Aeacus ("bewailing or earth borne"), in Greek legend, ancestor of the Aeacidae, was the son of Zeus and Aegina, daughter of the river-god Asopus. His mother was carried off by Zeus to the island of Oenone, which was afterwards called by her name.
When Aeacus' kingdom had a horrific plague, he prayed to Zeus for help. The king of the gods changed the local ants into people (Ovid, Met. vii. 520), who were called Myrmidones.
Aeacus ruled over his people with such justice and impartiality that after his death he was made judge of the lower world together with Minos and Rhadamanthus. Rhadamanthus judged the souls of Asiatics, Aeacus judged Europeans and Minos had the deciding vote. By his wife Endeis he was the father of Telamon and Peleus. By Psamathe, he fathered Phocus.
His successful prayer to Zeus for rain at a time of drought (Isocrates, Evagoras, 14) was commemorated by a temple at Aegina (Pausanias ii. 29). He himself erected a temple to Zeus and helped Poseidon and Apollo to build the walls of Troy.
From an old 1911 Encyclopedia