Many of the Waitomo caves also have stunning glowworm displays.
The New Zealand Glowworm (Arachnocampa luminosa) is a two-winged insect (fungus gnat) at the "larva" stage of its life-cycle. It lives in dark damp places and emits light to attract flying insects for food.
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.
Sticky substances on the lines trap insects and these are drawn up and devoured. They remain in this larva stage for about nine months and grow from 2mm to over 25mm in length.
They feed only in the larval stage and store sufficient food or energy to survive the pupa and adult stages.
The adult resembles a slightly enlarged mosquito.
The glowworm feeds mainly on midges and other airborne insects attracted by its 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 have a predator lurking. The glowworms "trick" the midges into "thinking" they're outside and then trap them.
To catch these flying insects, each glowworm lets down long sticky lines. One glowworm can have as many as 70 lines up to 20cm long. These lines are strong, elastic and beaded with very sticky glue. Once the insects get caught the glowworm senses the movement and pulls up the line and the struggling insect.
Glowworms can only survive in very damp dark places. They need a habitat with a horizontal ceiling or ledges, where they can hang their feeding lines, and sheltered places where wind does not dry them out or tangle their lines.
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 produce heat in our bodies.
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