Glorious glowworms

Last updated 14:25 07/02/2013

Glowworms are well-known to many New Zealanders, their soft blue-green light a beautiful night-time experience.  But how many of you knew that they are in fact the larvae of the fungus gnat?

Glowworms are creatures that truly do have the sun shining out of their bums.  Many of us may have experienced their presence in the bush or in caves such as the infamous Waitomo Glowworm Caves near Te Kuiti.  They provide a ghostly soft light and are truly beautiful to behold ... but take a closer look.

Glow worm snare

The beautiful web of the glowworm is a sticky trap for night-time flying insects. (photo: DOC).

Glowworms (Arachnocampa luminosa) are not worms at all, but the larvae (maggot) of a creature called the fungus gnat.  Their larval form is a long slimy worm-like creature that grows about the size of a matchstick, and hangs suspended in a transparent tube strung between two points (a bit like a hammock).  Underneath this hammock, the glowworm suspends lines of silk with tiny sticky droplets of mucus that are usedGlow worm adult like fishing lines to capture flying prey.  Flying insects are attracted to the glowing light emitted by the glowworm, and crash into the sticky threads, which are then reeled in so that the catch can be eaten by the glowworm. 

Glowworms have a kidney-like organ that they use to produce their distinctive blue-green light.  All stages of a glowworm's life cycle (except for the egg) can emit a light. The life cycle of a glowworm is such that the glowworm part is the longest, lasting up to nine months,  before the glowworm pupates and becomes a fungus gnat. The adult fungus gnat has no mouthparts and lives only for a few days, enough time to mate and lay eggs, creating a new generation of night-hunter glowworms.

The adult glowworm (the fungus gnat) bears little resemblance to it's larval form.

Glowworms are nice part of our natural culture, the things some of us discovered on a cool clear night in banks next to the track in the rich-smelling native bush, perhaps chanced upon while inspecting a local cave, or perhaps the focus of a visit to see them directly. 

My first glowworm encounter occurred on the West Coast, during a family trip where Mum and Dad convinced our teachers (my brother Tony and I were 10 and 12 years old) that we could be excused from school with the condition that we both wrote a diary of our travels.  I still remember it vividly.  While on the Coast, we visited Franz Josef and decided to do the short walk to the glowworms in the nearby bush.  Seeing the creatures up close and personal, with their chandelier-like threads and crystals hanging down, was fascinating.

More memorable was mum (a bit short-sighted) who couldn't see exactly where we were looking. "Where?" she said, peering in the dark past a bunch of tourists to see what we were looking at. "There!" we said. "Oh, there!" she replied, poking her finger out to point at where she had spotted them. Her finger however must have got too close, because as she did so a dozen little blue-green lights were immediately extinguished.  This story has been the source of much mirth over the years, but I wanted to reassure mum that she wouldn't have squished them, the glowworms would simply have retreated into crevices in the bank.

Glowworm boat cruise (photo: Waitomo Wanderer)

The Waitomo glowworm experience is a sight to behold indeed. (Photo: Waitomo Wanderer)

I still get a thrill when I chance upon glowworms, and a few years ago I was lucky enough to visit the Waitomo Glowworm Caves, a place that tourists have visited since the 1880s.  Sitting in the peaceful silence of a boat while watching a cave ceiling dottered with thousands of glowworms is quite a soulful experience indeed.  You can have a look at the Waitomo experience yourself in the video below:

Have you seen glowworms? Did you know they were the young of the fungus gnat? Where's your favourite place to spot them?

Please feel free to email me to send me your questions, feedback, ideas or photographs for In Our Nature blog posts. You can also join the In Our Nature Facebook page.

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