glowworm

[gloh-wurm] /ˈgloʊˌwɜrm/
noun
1.
the wingless female or larva of the European beetle, Lampyris noctiluca, which emits a sustained greenish light.
2.
any of various other beetle larvae or wingless females that emit a glow rather than a flash of light.
Origin
1300-50; Middle English. See glow, worm
British Dictionary definitions for glow-worm

glow-worm

noun
1.
a European beetle, Lampyris noctiluca, the females and larvae of which bear luminescent organs producing a greenish light: family Lampyridae
2.
any of various other beetles or larvae of the family Lampyridae
See also firefly (sense 1)
Word Origin and History for glow-worm
n.

early 14c., from glow (v.) + worm (n.).