A son of Amphiaraus and Eriphyle, and brother of Amphilochus, Eurydice, and Demonassa.1 His mother was induced by the necklace of Harmonia, which she received from Polynices, to persuade her husband Amphiaraus to take part in the expedition against Thebes.2 But before Amphiaraus set out, he enjoined his sons to kill their mother as soon as they should be grown up.3

When the Epigoni prepared for a second expedition against Thebes, to avenge the death of their fathers, the oracle promised them success and victory, if they chose Alcmaeon their leader. He was at first disinclined to undertake the command, as he had not yet taken vengeance on his mother, according to the desire of his father. But she, who had now received from Thersander, the son of Polyeices, the peplos of Harmonia also, induced him to join the expedition. Alcmaeon distinguished himself greatly in it, and slew Laodamas, the son of Eteocles.4

When, after the fall of Thebes, he learned the reason for which his mother had urged him on to take part in the expedition, he slew her on the advice of an oracle of Apollo, and, according to some traditions, in conjunction with his brother Amphilochus. For this deed he became mad, and was haunted by the Erinyes. He first came to Oicles in Arcadia, and thence went to Phegeus in Psophis, and being purified by the latter, he married his daughter Arsinoe or Alphesiboea,5 to whom he gave the necklace and peplos of Harmonia. But the country in which he now resided was visited by scarcity, in consequence of his being the murderer of his mother, and the oracle advised him to go to Achelous. According to Pausanias, he left Psophis because his madness did not yet cease. Pausanias and Thucydides6 further state, that the oracle commanded him to go to a country which had been formed subsequent to the murder of his mother, and was therefore under no curse.

The country thus pointed out was a tract of land which had been recently formed at the mouth of the river Achelous. Apollodorus agrees with this account, but gives a detailed history of Alcmaeon's wanderings until he reached the mouth of Achelous, who gave him his daughter Callirrhoe in marriage. Callirrhoe had a desire to possess the necklace and peplos of Harmonia, and Alcmaeon, to gratify her wish, went to Psophis to get them from Phegeus, under the pretext that he intended to dedicate them at Delphi in order to be freed from his madness. Phegeus complied with his request, but when he heard that the treasures were fetched for Callirrhoe, he sent his sons Pronous and Agenor7 or, according to Pausanias,8 Temenus and Axion, after him, with the command to kill him. This was done, but the sons of Alcmaeon by Callirrhoe took bloody vengeance at the instigation of their mother.9

The story about Alcmaeon furnished rich materials for the epic and tragic poets of Greece, and their Roman imitators. But none of these poems is now extant, and we only know from Apollodorus,10 that Euripides, in his tragedy Alcmaeon, stated that after the fall of Thebes he married Manto, the daughter of Tiresias, and that he had two children by her, Amphilochus and Tisiphone, whom he gave to Creon, king of Corinth, to educate. The wife of Creon, jealous of the extraordinary beauty of Tisiphone, afterwards sold her as a slave, and Alcmaeon himself bought her, without knowing that she was his daughter.11

Alcmaeon after his death was worshiped as a hero, and at Thebes he seems to have had an altar, near the house of Pindar,12 who calls him his neighbor and the guardian of his property, and also seems to suggest that prophetic powers were ascribed to him, as to his father Amphiaraus. At Psophis his tomb was shown, surrounded with lofty and sacred cypresses.13 At Oropus, in Attica, where Amphiaraus and Amphilochus were worshiped, Alcmaeon enjoyed no such honors, because he was a matricide.14 He was represented in a statue at Delphi, and on the chest of Cypselus.15