(Ἰσμήνος), a son of Asopus and Metope, from whom the Boeotian river Ladon was believed to have derived its name of Ismenus. (Apollod. 3.12.6.) The little brooks Dirce and Strophie, in the neighbourhood of Thebes, are therefore called daughters of Ismenus. (Callim. Hymn. in Del. 77; comp. Euirip. Bacch. 519; Diod. 4.72.) According to other traditions, Ismenus was a son of Amphion and Niobe, who when struck by the arrow of Apollo leaped into a river near Thebes, which was called Ismenus, after him. (Apollod. 3.5.6; Plut. de Fluv. 2.)
[L.S]A Dictionary of Greek and Roman biography and mythology
Smith, William
A Dictionary of Greek and Roman biography and mythology. William Smith, LLD, ed. 1890