WHAT ARE GLOW WORMS?

NZ glowworms are cousins to Aussie glowworms which have a very similar appearance. New Zealand glowworms are larger and have bigger lights. They seem to also thrive in much larger colonies possibly due to our environment and climate.

On a PADDLE BOARD ROTORUA Glowworm tour in Rotorua, New Zealand, you will not only find out more about these fascinating and almost magical little creatures, but you will view them up close in their natural habitat. 

New Zealand glowworms live all over New Zealand; they’re found in forest settings, often on damp overhanging stream banks and very commonly in caves (like ours) which seem to give the glowworms the best habitat of all.

The “worm” you see on the ceiling of our cave is the larval stage of a fungus gnat fly. The adult fungus gnat looks a little like a mosquito without a proboscis (their stabby thing).

Glowworm light is made from a biochemical reaction called bioluminescence which takes place at the terminal end of the renal glands or malphigian tubules of the larval glowworm. Energy to make the light is sourced from an energy rich protein, ATP which is manufactured there. Glowworms produce ‘cold’ light, a pure light with almost no associated heat.

Glowworms can turn off their lights. They may do this when there is too much bright light (from the sun or a torch) or to ‘hide’ if disturbed. Sudden loud noises often make them glow brighter.

The glowworm larva uses the light at its tail end as an irresistible lure to attract small flying insects lost in the darkness of the cave. Adult females can also produce a light at their tail which may help to attract a mate.When glowworm larvae hatch from eggs, the first to emerge eat later emerging siblings, this gives them a food supply and enables them to crawl away from the egg cluster to establish their own hammock and feeding lines.

The glowworm makes its home in the cave by attaching a silk hammock to the cave ceiling. To catch food, the glowworm larva builds a network of silk threads that hang down vertically all around, and also within reach of its hammock. As the glowworm extrudes each line from its silk glands, it places droplets of very sticky mucus over the thread line. A lost insect will fly towards the larva’s light lure and into a tangle of sticky silk threads and rarely escapes. The glowworm feels the tug of a struggling insect and reaches out of the hammock to haul up its meal. Insects caught in the glowworm’s lines are held there, stuck in the sticky acid mucus until the glowworm is ready to feed.

Glowworms are very territorial and can sometimes be seen fighting for space. They may eat one another; sometimes a glowworm is pushed off the ceiling and lands in the water or cave floor below.

Glowworms thrive in lake caves because lapping waters edge transports emerging aquatic insects into the cave. Once they emerge, they fly about the cave and are attracted to the glowworm’s light. In New Zealand aquatic insects emerge most months of the year providing a steady food source for glowworms. A healthy unpolluted lake generates lots of food.

Glowworm life cycle

  • Egg stage – 22 days
  • Larval stage – 9 to 12 months (this is when all the feeding occurs)
  • Pupal stage – 12-13 days
  • Fly stage – 2-4 days (glowworm flies cannot feed, they exist simply to mate and produce eggs to begin the next generation).
Matt Barnard