“You wouldn’t pay to come if we told you the caves were full of maggots so we call them ‘glow worms’,” said our guide. True enough. But in reality, the glowing strings from the larvae of the insect called arachnacampa luminosa are magnificent to behold, even if the larvae look just like slimy caterpillars.
Our blessedly small group of eleven headed for Mangawhitikau cave, a privately owned cave, and at 7 km long the longest cave in New Zealand. (In New Zealand, whoever owns the surface of the land also holds the rights to anything below and in the earth beneath.) About 200 meters into our first foray into Mangawhitikau we stopped to marvel over the silken, luminescent strings of a few dozen glow worms. Later, our group of eleven sat spellbound in a raft as the guide towed us down a subterranean river, through a small cavern carpeted with blue-green points of luminescence. In the complete darkness (no headlamps, no cameras, no talking) it was easy to feel disembodied and imagine we floated through a strange, magical new universe. The only sound came from a waterfall gurgling loudly at the end of the underground river.
As mesmerizing as the glow worms were, we learned that these larvae – a halfway phase in the insect’s life – had a very basic purpose for their glow: survival. Their light is the product of a biochemical reaction called bioluminescence. The silk threads spun by the larvae hang like glowing, sticky strands of a curtain to catch other insects for food. Thus, the larvae act somewhat between an insect and a spider: the glowing strands use the light to attract insect prey, and the stickiness of the threads trap the hapless prey as a spider’s web. Yet, similar to other insects, the larvae eventually spin themselves into a pupae, from which they eventually emerge as adults to start the procreative process once again. We learned that while these glowing larvae can be found in dark corners of the forest, they thrive best in caves, and can be found in subterranean chambers throughout New Zealand.
Photos as noted from Spellbound Glowworm & Cave Tours, Waitomo, New Zealand, www.glowworm.co.nz.
Post Script: Rafting the Tongariro River
We took a hugely different half-day rafting trip down the Tongariro River south of Lake Taupo (pronounced “toe-paw”: 3 hours, 14 km and 52 Class 3 rapids later we were exhausted but exhilarated. As you can see we got soaked, but it was great fun. Remarkably, the Tongariro is so pure you can drink directly from it — which we did. Lovely, fresh,, clear water! We highly recommend the group we went with, Rafting New Zealand.
Photos courtesy of Rafting New Zealand, Turangi, NZ, www.rankers.co.nz.