The light they emit comes from their waste which in turn attracts insects, their food.
"Ahhh!" we go to another fascinating revelation in what had already been a surreal adventure that is partly historical, geological, physical and unbelievable.
We are in Ruakuri - one of Waitomo's 300 known caves - and one of its premier attractions since the late 19th century, when local chief Tane Tinorau took English surveyor Fred Mace into the cave system.
With Josh is his guide buddy Andrew, aka "Monkey", a mulleted and affable 22-year-old John Key lookalike who explains that the name Ruakuri means "den of dogs".
Legend has it that this cave system was named after a young bird hunter who was attacked by a group of wild dogs guarding the cave nearly 500 years ago. He fled, dropping his catch of birds, but his people came back, killed the dogs and ate them.
After earlier safety demonstrations and explanations of how to use our various abseiling devices, we make a seemingly endless 40m - or 10-storey - abseil into Ruakuri's bowels.
The descent is a lot more nerve-racking and vertigo-inducing than it was on the practice hill a few moments earlier with a gap squeeze - the first of many we will do - at about 25m in the air.
But we all safely hit the ground in the tomo, a still environment with heavy air, where the sound of waterfalls seems ever-present and your breath shows with every utterance.
Our knowledgeable guides then talk to us about the surrounding limestone formations created about 30 million years ago when Wai(water)tomo(hole or shaft) was beneath the sea.
Who knew that limestone is actually a fossil rock consisting of the remains of millions of marine animals broken down by the sea into tiny particles that slowly settled on the seabed over millions of years ?
"I often marvel at the strangeness of it all," says Josh, matter-of-factly.
But what I find strange - and a heck of a lot of fun - comes not long after when we are connected to a flying fox and sent screaming into a cavern in complete darkness.
This is followed by an even more surreal blackwater rafting experience, which the Legendary Blackwater Rafting Company has prided itself on for the past 22 years.
The water - which is normally somewhere between 10C and 14C - is cold, but let's face it you're going to get really wet down here and have a ball doing so.
You'll also spend time crawling under waterfalls, up waterfalls, through crevices and, if you're lucky, you may have the chance to swim with one of Ruakuri's resident eels, Cecil, who was certainly not shy of human company during our visit.
Perhaps the only thing missing in our tubing journey through what seemed like a valley of stellar-like glowworm constellations and stalactite formations was the opening theme to Star Trek and ancient cave paintings of mythical animals, which I was half-expecting to see.
Having ditched our tubes, there's still a lot of squeezing, sliding, crawling and rock climbing to do to get out of the cave system and, despite my claustrophobia, I can see the attraction in the adventure of caving which Monkey pointed out to me earlier.
This is an extremely fun, value-for-money and educational five hours.
When given your two exit options from what is known as The Abyss, take the "pools of doom" over the "path of tranquillity" for one last decent shot of adrenalin before you enjoy a hot shower, bagels and soup.
DOING WAITOMO
• Takes 5 hours (beginner level).
• You must be 16 years and weigh more than 45kg.
• Need swimwear and towel.
• Water temperature 10-14C.
• Wetsuits and footwear provided.
• 8 people per tour maximum.
Contact: The Legendary Blackwater Rafting Company on 0800 228 464.
ACCOMMODATION:
Woodlyn Park, 1177 Waitomo Valley Rd
Owner Barry Weathers says he was inspired by travelling the world and staying in five-star hotels which were pretty much the same design wherever he went. His response was Woodlyn Park - an almost theme park-like assortment of accommodation options spread over 3.6ha and less than a kilometre from Waitomo's hub.
Keeping with my subterranean theme and caving exploits earlier in the day, I chose the hobbit unit - one of two at the reserve. The unit is dug into the ground, has curved ceilings, rounded windows and doors and sack cloth for curtains but caters for the likes of a Gandalf rather than a Frodo.
If Middle Earth isn't your thing, you can always choose the plane unit - a 1950s Bristol from Waihi Airport that has been made into a comfortable lodging.
There's also the "Waitanic" boat unit, a World War II Fairmile sub hunter fitted with chandeliers, moulded ceilings and shiny brass portholes.
EATING
Huhu, 10 Waitomo Caves Rd
I was hoping to find our native huhu grub or wetas on the menu but was sadly disappointed. So I had to make do with a pea and mint soup with a couple of slices of rewena (Maori bread) - sublime.
This was followed by a free-range chicken breast with pancetta stuffed with romano cheese on mashed potato, asparagus and cherry tomatoes as I enjoyed the views over Waitomo Village from a warmly sunlit deck.
While the menu is focused on "small plates," meaning each dish is based on just one or two key ingredients, I was surprisingly content and had to pass on the caramelised rum bananas and Piopio strawberry cheesecake.
Lonely Planet says you won't be disappointed if you eat every meal at Huhu - just don't be surprised at the Ponsonby Rd prices.
