Elachyophtalma semicostalis is a moth in the Bombycidae family. It was described by Rothschild in 1920. It is found in New Guinea. The wingspan is 48–58 mm. The forewings are thinly scaled with sooty black-brown, the basal half with an olive tinge and the basal three-fifths of the costal area orange-buff. The basal two-thirds of the hindwings is sooty black-brown, the outer two-fifths orange-golden.