Glow Worm Tour night walk: The Blue Mountains' secret attraction

Glow worms have probably been glimmering on the sandstone overhang of a fern-filled gully near Berambing in the Blue Mountains for a million years. Yet they went unnoticed by local residents until one evening in 2015 when an inebriated partygoer took the wrong path home and found herself amid a wondrous galaxy of blue-green dots of light.

The fabulous find has been somewhat secret since, but property owner Jochen Spencer recently decided to share the glow worms on small-group tours. And so I find myself standing by a lonely roadside as a brisk wind tickles the trees and tosses an almost-full moon between their branches. Jochen's car looms out of the dark and crunches onto the verge. Headlights die and a dark figure emerges like a film-noir detective.

We set off uncertainly down a track, our wobbling headlamps briefly illuminating tree trunks and rocks. It's a short walk into the glow-worm gully, but you need confidence and good knee joints to negotiate the uneven and slippery surfaces in near darkness. This is no slick tourist attraction. Access is endearingly amateurish, with steps hacked out of rocks or created from a rickety assemblage of Mad Max planks held together with outsized nails. Railings look as if they'd collapse if anyone stumbled against them. Vast gumtrees are outlined against the moonlit sky, and an unseen waterfall gushes.

I'm guided as much by Jochen's voice as by my headlamp. He has certainly become well acquainted with glow worms, which he explains aren't worms at all but the name given to either flies or beetles in various parts of the world. In Australia, they're one of eight species of primitive fly called a fungus gnat, whose light is produced by a chemical reaction between oxygen in the air and enzymes and pigments in the insect's abdomen.

"The name glow worms sounds almost poetic, but actually they're larvae, and closer to maggots than worms," says Jochen. "They have a mouthful of teeth and don't do much but eat other insects – and each other."

The larvae grow for nine months before hatching gnats that only last a couple of days; they have no mouths and can't eat, but before starving lay eggs that start the bizarre cycle of life all over again. And yet these sinister-sounding gnats seem like magical faerie creatures when we first glimpse them on a rock face, glowing in a steady pale blue as if someone has draped Christmas lights along the path.

Later, we sit on rocks by the stream that runs through this gully, turn off our headlamps, and fall silent. There isn't much you can say about such a peculiar and wondrous incarnation of nature. The glow worms are constellations on the gully's sandstone, pretty in the darkness.