underwing

[ uhn-der-wing ]

/ ˈʌn dərˌwɪŋ /

one of the hind wings of an insect.

any of several noctuid moths of the genus Catocala, characterized by red-, yellow-, or orange-banded hind wings.

Origin of underwing

First recorded in 1525–35; under- + wing

The first thing I ever got from her was a lovely look, the first time ever I set eyes on her she came with an underwing moth.

Slippy McGee, Sometimes Known as the Butterfly Man |Marie Conway Oemler
Underwing, un′dėr-wing, n. a moth with conspicuous underwings, esp.

Chambers's Twentieth Century Dictionary (part 4 of 4: S-Z and supplements) |Various

underwing

/ (ˈʌndəˌwɪŋ) /

the hind wing of an insect, esp when covered by the forewing