Like fireflies, the spectacular worms of New Zealand’s Waitomo Caves glow by breaking down a light-emitting protein. But unlike the yellow mating flashes of fireflies, the glow worms’ steady blue light has a more insidious purpose: it’s bait.
The strategy is simple. Many of the glow worms’ prey are insects, including moths, that navigate by starlight. With imposter stars all around, the insects become disoriented and fly into a waiting snare. Once the victim has exhausted itself trying to get free, the glow worm reels in the catch.
The prey is typically still alive when it arrives at the glow worm’s mouth, which has teeth sharp enough to bore through insect exoskeletons.
Glow worms live in colonies, and researchers have noticed that individual worms seem to sync their lights to the members of their colony, brightening and dimming on a 24-hour cycle. There can be several colonies of glow worms in a cave, and studies have shown that different colonies are on different cycles, taking turns at peak illumination, when they’re most attractive to prey.
Not surprisingly, the worms glow brighter when they’re hungry.