FIREFLY
firefly, lightning bug
(noun) nocturnal beetle common in warm regions having luminescent abdominal organs
firefly, fire beetle, Pyrophorus noctiluca
(noun) tropical American click beetle having bright luminous spots
Source: WordNet® 3.1
Etymology
Noun
firefly (plural fireflies)
Any beetle of the family Lampyridae, which exhibit bioluminescence during twilight.
Synonyms
• (beetle): lightning bug
Source: Wiktionary
Fire"fly`, n.; pl. Fireflies (. (Zoöl.)
Definition: Any luminous winged insect, esp. luminous beetles of the family
Lampyridæ.
Note: The common American species belong to the genera Photinus and
Photuris, in which both sexes are winged. The name is also applied to
luminous species of Elateridæ. See Fire beetle.
Source: Webster’s Unabridged Dictionary 1913 Edition