glowworm

Short definition from Wiktionary

Noun

1. 1
   The larva or wingless grub-like female of a beetle from the families Phengodidae or Lampyridae that gives out a green light from its abdomen.
2. 2
   A carnivorous gnat larva in the keroplatid genus Arachnocampa that spins threads to capture insects attracted by its glow.