Ethmia subnigritaenia is a moth in the Depressariidae family. It is found in Mexico. The length of the forewings is 11.4-12.3 mm. The ground color of the forewings is whitish gray, infused with dark grayish clouding, slightly less so on the dorsal and terminal areas. The ground color of the hindwings is semitranslucent whitish, becoming pale brownish in the apical area.