From Smith's Dictionary of Greek and Roman Biography and Mythology

DANAIDES

the fifty daughters of Danaus, whose names are given by Apollodorus (ii) and Hyginus, though they are not the same in both lists. They were betrothed to the fifty sons of Aegyptus, but were compelled by their father to promise him to kill their husbands, in the first night, with the swords which he gave them. They fulfilled their promise, and cut off the heads of their husbands with the exception of Hypermnestra alone, who was married to Lynceus, and who spared his life. According to some accounts, Amymone and Berbyce also did not kill their husbands.

Hypermnestra was punished by her father with imprisonment, but was afterwards restored to her husband Lynceus.

The Danaides buried the corpses of their victims, and were purified from their crime by Hermes and Athena at the command of Zeus. Danaus afterwards found it difficult to obtain hus­bands for his daughters, and he invited men to public contests, in which his daughters were given as prizes to the victors

Pindar mentions only forty-eight Danaides as having obtained husbands in this manner, for Hypermnestra and Amymone are not included, since the former was already married to Lyncetis and the latter to Poseidon. Pausanias mentions that Automate and Scaea were married to Architeles and Archander, the sons of Achaeus.

According to the Scholiast on Euripides, the Danaides were killed by Lynceus together with their father. Notwithstanding their purification mentioned in the earlier writers, later poets relate that the Danaides were punished for their crime in Hades by being compelled everlastingly to pour water into a vessel full of holes.

Strabo and others relate, that Danans or the Danaides provided Argos with water, and for this reason four of the latter were worshipped at Argos as divinities and this may possibly be the foundation of the story about the punishment of the Danaides. Ovid calls them by the name of the Belides, from their grandfather, Belus; and Herodotus (ii), following the tales of the Egyptians, says, that they brought the mysteries of Demeter Thesmophoros from Egypt to Peloponnesus, and that the Pclasgian women there learned the mysteries from them.