In caves at Waitomo, on the North Island of New Zealand, the ceiling looks like a starry night sky. Each point of blue light is a living creature.

These are glowworms — not worms, but the larvae of a fungus gnat, Arachnocampa luminosa, found only in New Zealand. Each larva hangs down dozens of silk threads covered in sticky droplets, and glows to attract insects, which get caught in the threads.

The light comes from a chemical reaction in the larva's body. Hungry larvae glow brighter.

Visitors glide through the caves by boat, in silence, because noise and light can make the glowworms dim. The caves have been explored and guided by local Māori people since the late 19th century.