A daughter of Hypseus, a Lapith, and the third wife of Athamas. She is by him the mother of Leucon, Erythrus, Schoeneus, and Ptous,1 or of Sphincius and Orchomenus.2

Hyginus3 relates the following story: when Athamas heard that his second wife Ino had not died and was living as a votary of Dionysus in the ravines of Parnussus, he secretly send for her. Themisto, robbed of her marriage, was determined to kill Ino's children. She confided in Ino, not knowing her identity and believing her a captive, telling to her to dress her children in white garments, and Ino's children in black, so that she might recognize them at night. Ino exchanged the children's clothes and in consequence Themisto killed her own children. When she became aware of her mistake she took her own life.