UNDERWING

underwing

(noun) moth having dull forewings and brightly colored hind wings

Source: WordNet® 3.1

Etymology

Noun

underwing (plural underwings)

A hind wing on an insect.

A member of the genus Catocala, a nocturnal moth which usually has brightly coloured underwings.

(ornithology) The underside of a bird's wing.

Source: Wiktionary

Un"der*wing`, n.

1. (Zoöl.)

Definition: One of the posterior wings of an insect.

2. (Zoöl.)

Definition: Any one of numerous species of noctuid moths belonging to Catocala and allied genera, in which the hind wings are banded with red and black or other conspicuous colors. Many of the species are called red underwing.

Source: Webster’s Unabridged Dictionary 1913 Edition