Glow worms love damp, dark conditions with little wind, like here the Ananui/Metro cave system, perhaps the largest colony of glowworms in the South Island. The light is the result of a chemical reaction between luciferin (a waste product), the enzyme lucifarse, ATP and oxygen. It attracts prey which get caught in the sticky silk threads. The worms live for only nine months, after which they pupate into a fungus gnat.