There are many miracles in the country of the Long White Cloud, and in this article I would like to talk about the miracle often seen at nights, miracle that illuminates New Zealand’s forests and caves – the glowworms. Known by the scientific name Arachnocampa luminosa, they knit their silk threads on the cave sets and in tree roots, illuminating space around them like thousands of tiny flashlights.
I saw fireflies for the first time in Waipu cave. We stopped there on our way to Whangarei, and I was very happy that we did. Many tourists who plan thoroughly their visit in NZ include this stalactite cave in their itinerary, and after visiting it myself I understand why. I strongly advise you not to pass on Waipu cave. For a visit you will need sandals to walk in water, clothing which you won’t hesitate to spoil, and a flashlight. The great thing about this cave is that it was not “civilized”. There are no boardwalks or electric lights and it feels untouched and prehistoric. When you get far enough from the entrance for the outside light to vanish, turn off your flashlight and look up… I will never forget this sight of starry sky. When your eyes will get used to the darkness, the light from the glowworms is bright enough to see where you walk.
The second time I saw the glowworm wonder was in Trounson Kauri Park, which is located in western Northland, 40km north of Dargaville. I was there during Kiwi breeding season, and a park ranger advised me to go for a night walk in the park for kiwi spotting. So I went for a night walk in Trounson Kauri Park, and while looking for kiwis I stumbled upon a huge Kauri stump which was settled by a glowworm colony. In the dark it looked like a magic house with many rooms with lights turned on.
The big question, however, is why and how glowworms glow, and why evolution haven’t denied them this non camouflaging quality (glowworms are seen from long distance in the dark, which may make them more vulnerable)?
It turns out that glowworms managed to accomplish something that scientists are still unable to do and only recently got closer to achieving – they use almost 100% of their energy for lighting! Let me explain: for example in the usual light bulb less than 10% of the energy is used for lighting, while the rest of the energy is wasted as heat. Glowworms however emit “cold light”. After all, they can not afford to spend most of their energy on heating because they would virtually cook themselves!
The organ that is responsible for light emission in glowworms has very complicated structure, and the chemical processes which take place are complicated even more. They engage oxygen, nitric acid, adenosine triphosphate molecule (ATP), and Luciferin pigment. The result is – bioluminescence – difficult word to describe this complex process! The organ emits light when there is enough oxygen, and stops emitting when oxygen run out. Glowworms are also capable of scintillating, which depends on nitrogen supply to the organ.
Glowworms glow for various reasons. They produce substances in their bodies which make them an unpleasant food to predators and their glow serves as indicator to it. Another reason for glowing is to attract the opposite sex. Each mature glowworm scintillates in a unique way, so that their mates can distinguish them from other glowworms. Scientific research shows that female glowworms choose their males according to their flashing. Turns out that two types of glowworm females prefer males with brighter luminescence and a higher frequency of flashing. Hungry glowworms also shine brighter than usual to attract other insects, which fly towards bright light and directly into a trap. They get caught in silk threads and eaten by the glowworms.
The ability to shine remains with the glowworm during all stages of its development: larvae, pupae and adulthood. People in many countries used glowworms as a natural jewelry and a tiny source of light.
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