Glow worms a highlight!


The Kiwi Conservation Club and Iron Duke Cubs group made night visits to the Brook Sanctuary to check out the glow-worms.

The children said it was very exciting to walk through the dark forest with torches and find the hundreds of glow worms shining out along the track. Most of them had never seen glow-worms before and really enjoyed the treat of hearing the Morepork calling in the trees above the visitor centre.New Zealand’s glow-worms

What is a glow-worm?
None of the world’s glow-worms are true worms. In the northern hemisphere the name is used for beetles that fly around at night with their tail-lights flashing.
In New Zealand and Australia, glow-worms are the larvae (maggots) of a special kind of fly known as a fungus gnat. Fungus gnats look rather like mosquitoes, and most feed on mushrooms and other fungi. However, a small group of fungus gnats are carnivores, and the worm-like larvae of these species use their glowing lights to attract small flying insects into a snare of sticky threads. One species,Arachnocampa luminosa, is found throughout New Zealand, and others occur in Australia.
Hundreds of Arachnocampa larvae may live side by side on a damp sheltered surface, such as the roof of a cave or an overhanging bank in the forest. Their lights resemble a star-filled night sky. Māori call them titiwai, which refers to lights reflected in water.
Glow-worms need damp places, where the air is humid and still, to construct their snares. Caves and old mining tunnels are ideal. In the forest glow-worm snares are commonest on moist banks beside a stream or in a ravine.
Small midges are the usual prey of glow-worms, but all sorts of flying insects get trapped in the sticky snares, including mayflies, caddisflies and moths. Forest glow-worms may also trap spiders, plant hoppers and even millipedes. The glow-worm simply cuts free any prey that is too large, or unwanted.
Adult glow-worm flies are never caught in the snares – they are not attracted to the light, and even if they brush against the sticky threads they are strong enough to pull free.
Light display
The glow-worm’s tail-light shines from an organ which is the equivalent of a human kidney. All insects have this organ but the glow-worm has a unique ability to produce a blue-green light from it.
The chemical reaction that produces the light consumes a lot of oxygen. An airbag surrounds the light organ, providing it with oxygen and acting as a silvery reflector to concentrate the light.
A fungus gnat can glow at all stages of its life cycle (except as an egg), but the larva has the brightest light.
In caves the insects light up at any time of the day or night. Outdoor glow-worms start glowing shortly after dark and usually shine all night. Sometimes when a glow-worm is disturbed its light seems to go off suddenly. This is the larva slithering into a crevice, hiding its light. It actually takes several minutes for the larva to shut off the light.