- either of the pair of hind wings of an insect
- any of various noctuid moths (esp. genus Catocala) having brightly colored hind wings that are hidden under drab forewings except during flight
See underwing in American Heritage Dictionary 4
- One of a pair of hind wings of an insect, such as a moth.
- Any of various noctuid moths of the genus Calocala, having brightly colored hind wings visible only during flight.
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