Many of the Waitomo caves have stunning glowworm displays.
The New Zealand Glowworm (Arachnocampa luminosa) is a two-winged insect (a fungus gnat) at the larval stage of its life-cycle. It lives in dark, damp places and emits light to attract flying insects to feed on.
The glowworm's whole life cycle takes about 11 months. Eggs are laid in clutches of 30-40 on walls and ceilings. Within 20 days the young larvae hatch from the eggs, emitting a bright light and crawling upward until they reach a suitable area to hang their feeding lines.
The sticky feeding lines trap insects which are drawn up and devoured. They remain in this larval stage for about nine months and increase in length from 2mm to over 25mm.
Glowworms feed only in the larval stage and store sufficient food to survive to adulthood.
The adult resembles a slightly enlarged mosquito.
Glowworms feed mainly on midges and other airborne insects attracted by their light. En masse the glowworms mimic the stars in the night sky. All flying insects have a strong instinct to fly towards an open space and try to keep away from walls or vegetation that might conceal a predator. The glowworms "trick" the midges into "thinking" they're outside and then trap them.
To catch flying insects each glowworm lets down as many as 70 long sticky lines up to 20 cms long. The lines are strong, elastic and beaded with very sticky glue. As soon as an insect is entangled the glowworm senses the movement and pulls up the line.
Glowworms only survive in very damp, dark places. They need a habitat with horizontal surfaces to hang their feeding lines and shelter from wind to prevent the lines from drying out or tangling.
The light the glowworm emits is called bioluminescence.
Bioluminescence involves the mixing of four chemicals - ATP, adenosine triphosphate luciferin, luciferase and oxygen. The glowworm controls its light by reducing oxygen to the light organ. The light is the result of a chemical reaction and is similar to the way we make heat in our bodies.
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