Glowworm, the wingless, wormlike female or the larva of a beetle related to the firefly. The soft-bodied, flattish beetle is about one-half inch (13 mm) long; the larva is slightly longer. A greenish-blue, cold light is emitted from the female's abdomen and from the larva. In some species, the eggs also glow. For information on how the light is produced, .

The common glowworm is Lampyris noctiluca of the family Lampyridae.