Red underwing Meaning, Definition & Usage

  1. noun moth having dull forewings and red-marked hind wings
    Catocala nupta.

WordNet

Definitions
  1. (Zoöl.), any species of noctuid moths belonging to Catacola and allied genera. The numerous species are mostly large and handsomely colored. The under wings are commonly banded with bright red or orange.

Webster 1913