The passage dropped so low that I had to crawl. My knees slid through guano, my elbows scraped limestone, and my headlamp threw jumping shadows every time I moved. Jau had drawn me a map on the back of a candy wrapper — past the second bat roost, through a squeeze he called the throat. My pack barely fit. Then, on the far wall, in a crack where the rock gleamed with moisture, I saw it: green light.
Not bright like a torch. Not sharp like a screen. Just a faint, cold glow, as if a little piece of green moonlight had gotten trapped in the stone. I switched off my headlamp and let my eyes adjust. There, growing from a wedge of rotting wood pinned into the crack, was a cluster of tiny mushrooms, each one smaller than my thumbnail, quietly shining in the dark. I found it. The thing that should not be glowing.
I sat back and opened my notebook. I had seen living things make light before.
In the deep sea, one glow warns. Another lures.
So I did what people do when they are much too pleased with themselves: I decided I understood. One word — defense — and I closed the notebook.
And then my tidy little theory began to fall apart.
A small fly drifted into the green light. It did not veer away. It circled once, then landed right on one of the shining caps. I waited for the fungus to flash, or pulse, or snap shut. Nothing happened. The fly simply sat there.
Then another fly came. And another. They were not avoiding the light. They were following it.
I waited for the fungus to eat them. Instead, the flies left.
I pulled out my hand lens and leaned closer. Their legs were dusted with something pale. Poison? Dust?
Then one fly lifted off and vanished into a crack in the wall. Another crawled into a dark seam where water dripped down the rock.
Not poison.
Spores.
The fungus was not trying to frighten anything. It was drawing them in. The glow was not a warning. It was bait.
Not to catch, to carry.
This mushroom is fishing.
The same trick as the anglerfish — but with a different ending.
I opened my notebook and drew one slow line through the word defense. Being sure is dangerous.
I could almost hear Dr. Okafor's voice beside me in the dark. "Those are YOUR categories, Marlowe." She was right. I had come into the cave carrying an answer with me. I had seen something familiar and rushed to give it a familiar meaning. I had almost forgotten to look.
The deep ocean and this cave are nothing alike, and yet both are full of bioluminescence. But the same glow does not always do the same job. I stood up too fast and cracked my head on a stalactite. Sat right back down, laughing.
Tomorrow I leave Borneo for a place I have been avoiding for three years: the cloud forests of Ecuador. A botanist has written to me about a plant that does something impossible. It moves. On purpose. Fast. The last time I went into a cloud forest, I got lost for nine hours and had to be rescued by a twelve-year-old. Still, some mysteries are worth following.
Nobody knows. I'd like to find out.
