"I'm going to end up a cripple," said Po.

"At least I won't have to hear your mother and father complain about what I did to you, since I don't expect to get out of here alive."

And then, suddenly, the light went dim. For a moment Sel thought it had gone out, but no — Po had stood up and lifted the stick to a vertical position, so that the tunnel where Sel was creeping along was now in shadow.

It didn't matter. Sel could see the chamber ahead. It was a natural cavern, with stalactites and stalagmites forming columns that supported the ceiling.

But they weren't the straight-up-and-down columns that normally formed when lime-laden water dripped straight down, leaving sediment behind. These columns twisted crazily. Writhed, really.

"Not natural deposits," said Po.

"No. These were made. But the twisting doesn't seem designed, either."

"Fractal randomness?" asked Po.

"I don't think so," said Sel. "Random, yes, but genuinely so, not fractal. Not mathematical."

"Like dog turds," said Po.

Sel stood looking at the columns. They did indeed have the kind of curling pattern that a long dog turd got as it was laid down from above. Solid yet flexible. Extrusions from above, only still connected to the ceiling.

Sel looked up, then took the stick from Po and raised it.

The chamber seemed to go on forever, supported by the writhing stone pillars. Arches like an ancient temple, but half melted.

"It's composite rock," said Po.

Sel looked down at the boy and saw him with a self-lighting microscope, examining the rock of a column.

"Seems like the same mineral composition as the floor," said Po. "But grainy. As if it had been ground up and then glued back together."

"But not glued," said Sel. "Bonded? Cement?"

"I think it's been glued," said Po. "I think it's organic."

Po took the stick back and held the flame of the lamp under an elbow of one of the twistiest columns. The substance did not catch fire, but it did begin to sweat and drip.

"Stop," said Sel. "Let's not bring the thing down on us!"

Now that they could walk upright, they moved forward into the cavern. It was Po who thought of marking their path by cutting off bits of his blanket and dropping them. He looked back from time to time to make sure they were following a straight line. Sel looked back, too, and saw how impossible it would be to find the entrance they had come through, if the path were not marked.

"So tell me how this was made," said Sel. "No toolmarks on the ceiling or floor. These columns, made from ground-up stone with added glue. A kind of paste, yet strong enough to support the roof of a chamber this size. Yet no grinding equipment left behind, no buckets to carry the glue."

"Giant rock-eating worms," said Po.

"That's what I was thinking, too," said Sel.

Po laughed. "I was joking."

"I wasn't," said Sel.

"How could worms eat rock?"

"Very sharp teeth that regrow quickly. Grinding their way through. The fine gravel bonds with some kind of gluey mucus and they extrude these columns, then bind them to the ceiling."

"But how could such a creature evolve?" said Po. "There's no nutrition in the rock. And it would take enormous energy to do all this. Not to mention whatever their teeth were made of."

"Maybe they didn't evolve," said Sel. "Look — what's that?"

There was something shiny ahead. Reflecting the lamplight.

As they got closer, they saw reflections from spots on the columns, too. Even the ceiling.

But nothing else was as bright as the thing lying on the floor.

"A glue bucket?" asked Po.

"No," said Sel. "It's a giant bug. Beetle. Ant. Something like — look at this, Po."

They were close enough now to see that it was six-legged, though the middle pair of limbs seemed more designed for clinging than walking or grasping. The front ones were for grasping and tearing. The hind ones, for digging and running.

"What do you think? Bipedal?" asked Sel.

"Six or four, and bipedal at need." Po nudged it with his foot. No response. The thing was definitely dead. He bent over and flexed and rotated the hind limbs. Then the front ones. "Climb, crawl, walk, run, all equally well, I think."

"Not a likely evolutionary path," said Sel. "Anatomy tends to commit one way or the other."

"Like you said. Not evolved, bred."

"For what?"

"For mining," said Po. He rolled the thing over onto its belly. It was very heavy; it took several tries. But now they could see much better what it was that caught the light. The thing's back was a solid sheet of gold. As smooth as a beetle's carapace, but so thick with gold that the thing must weigh ten kilos at least.

Twenty-five, maybe thirty centimeters long, thick and stubby. And its entire exoskeleton thinly gilt, with the back heavily armored in gold.

"Do you think these things were mining for gold?" asked Po.

"Not with that mouth," said Sel. "Not with those hands."

"But the gold got inside it somehow. To be deposited in the shell."

"I think you're right," said Sel. "But this is the adult. The harvest. I think the formics carried these things out of the mine and took them off to be purified. Burn off the organics and leave the pure metal behind."

"So they ingested the gold as larvae.»

"Went into a cocoon.»

"And when they emerged, their bodies were encased in gold."

"And there they are," said Sel, holding up the light again. Only now he went closer to the columns, where they could now see that the glints of reflection were from the bodies of half-formed creatures, their backs embedded in the pillars, their foreheads and bellies shiny with a layer of thin gold.

"The columns are the cocoons," said Po.

"Organic mining," said Sel. "The formics bred these things specifically to extract gold."

"But what for? It's not like the formics used money. Gold is just a soft metal to them."

"A useful one. What's to say they didn't have bugs just like these, only bred to extract iron, platinum, aluminum, copper, whatever they wanted?"

"So they didn't need tools to mine."

"No, Po — these are the tools. And the refineries." Sel knelt down. "Let's see if we can get any kind of DNA sample from these."

"Dead all this time?"

"There's no way these are native to this planet. The formics brought them here. So they're native to the formic home world. Or bred from something native there."

"Not necessarily," said Po, "or other colonies would have found them long before now."

"It took us forty years, didn't it?"

"What if this is a hybrid?" asked Po. "So it exists only on this world?"

By now, Sel was sampling DNA and finding it far easier than he thought. "Po, there's no way this has been dead for forty years."

Then it twitched reflexively under his hand.

"Or twenty minutes," said Sel. "It still has reflexes. It isn't dead."

"Then it's dying," said Po. "It has no strength."

"Starving to death, I bet," said Sel. "Maybe it just finished its metamorphosis and was trying to get to the tunnel entrance and stopped here to die."

Po took the samples from him and stowed them in Sel's pack.

"So these gold bugs are still alive, forty years after the formics stopped bringing them food? How long is the metamorphosis?"

"Not forty years," said Sel. He stood up, then bent over again to look at the gold bug. "I think these cocooned-up bugs embedded in the columns are young. Fresh." He stood up and started striding deeper into the cavern.

There were more gold bugs now, many of them lying on the ground — but unlike the first one they found, many of these were destroyed, hollowed out. Nothing but the thick golden shells of their backs, with legs discarded as if they had been.

"Spat out," said Sel. "These were eaten."