New Zealand's 'Glow-In-The-Dark' Cave is Powered By Flies!


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New Zealand's North Island is known for many things - it's active volcanoes, pristine beaches, waters that harbor about 8000 marine species as well as the rich Maori culture and heritage. However, none come even close to one of nature's most amazing and unique offerings - The Glowworm Grotto Cavern.

Located in Waitomo, a sparsely populated area in North Island's King County, the Glowworm Grotto is part of a labyrinth of caverns known as Waitomo Caves. In order to get to it, visitors seated in small boats or inner tubes, first have to traverse through a number of equally stunning caves that are home to some of the world's biggest and most stunning, stalactite and stalagmite formations.

But nothing prepares them for the amazing Glowworm Grotto - As they enter the pitch black cavern, it appears as though the sky filled with shining stars, has moved close enough for them to reach out and pluck one! As you may have guessed, these are not exploding balls of gas, but a species of fungus gnats that scientists call Arachnocampa luminosa or 'glowing spider bug'.

Endemic to New Zealand, the tiny flies that grow to just about 3 centimeters long, undergo the same four basic life stages as other insects - egg, larva, pupa and adult. While they glow in all except for the egg stage, it is during the larval stage, which also happens to be the longest span of their 6-12 month life cycle (depending on the availability of food supply) that the tiny creatures become really luminescent.

The 'glow', a chemical reaction between Luciferin, a chemical substance, oxygen and ATP (an energy carrying molecule found in all living creatures), helps the larvae to attract food - The hungrier they are, the brighter they shine through their transparent skin.

What is even more fascinating is how they capture the prey that gets attracted to the bright hue - As the moths, midges or other small insects come close, they get stuck to the dozens of long strands of mucus coated silk that the larvae has strategically laid down. Once that happens the sly insect pulls the silk strand up and slurps down the unsuspecting prey! The coolest part is that the larvae are very sensitive to disturbances and stop glowing if they sense any danger. Therefore to see it in its full glory, tourists have to maintain pin drop silence.

Since adult gnats have no mouths, their lifespan is limited to between 3-5 days, during which time they mate and lay eggs. The fortunate part is that these short-lived flies lay thousands of them at a time and since they are bad fliers, always within the same vicinity. This means that the supply of larvae in the Glowworm Grotto cavern is never in any danger of running out.

In fact, because the cave is so isolated, the only real threats to the group that thrives here, is from tourists that remove the larvae to get a closer look or from fellow gnats that try to take over their territory - an event that usually ends up in a fight where one group gets swallowed by the other. Fortunately these are rare occurrences and for now the famous fungus gnats of Glowworm Grotto seem to be flourishing and . . . glowing!


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  • Elliottover 4 years
    I think this is a very cool article because when the flies sense danger their glow goes away.
    • lyloxabofopuse
      lyloxabofopuseover 4 years
      OS cool i love it
      • tazmania
        tazmaniaover 4 years
        NZ RULES!!!!!!!! :)
        • sassy lassyalmost 5 years
          i love to learn about new zealand.
          • COOLalmost 5 years
            • Lilliealmost 5 years
              soooooooooooooo cool
              • Brooklyn Malmost 5 years
                That is so amazing!
                • best awsomealmost 5 years
                  • coolalmost 5 years
                    the best ever
                    • Honeyalmost 5 years
                      Teacher made us right down all vocab and definitions.