Nye (1975) stated:-
Orthoa is a junior objective synonym of Orthosia Ochsenheimer, 1816. Incorrect type-species designation: Phalaena incerta Hufnagel, 1766, a name not, originally included in Orthoa, and not linked with one of the, originally included names when cited by Tams, 1939, Entomologist 72:140.
Orthoa Billberg, 1820 an unjustifiable emendation of Orthosia Ochsenheimer, 1816; given by Kocak, 1981, Priamus 1 (1) : 22.
See: ORTHOSIA Ochsenheimer, 1816.
Poole (1989) included ORTHOA Billberg, 1820; MONIMA Hübner, 1821; CUPHANOA Hübner, 1821; SEMIOPHORA Stephens, 1829; TAENIOCAMPA Guenée, 1839; CYPHONOA Agassiz, 1847 (as CYPHONA on page 741); EUCHORISTEA Warren, 1910 (as EUCHORISTA on page 741); ERYTHROTIS Bryk, 1949; ANCATA Capuse, 1958; ANORTHOA Berio, 1980; CORORTHOSIA Berio, 1980; and MICRORTHOSIA Berio, 1980 as junior synonyms of ORTHOSIA Ochsenheimer, 1816.
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