There was the question of whether to build a fire. If you were stranded in the wilderness at night in the normal world, you would build a fire to stay warm and drive off predators. The situation was different in the micro-world. Erika Moll summed it up: “Insects are attracted to light. If we have a fire, it could draw predators from hundreds of meters away. I suggest we do not use our headlamps, either.”

It meant they would spend the night in total darkness.

As dusk turned into night, the world was drained of color, fading into grays and blacks. They began to hear a pattering, thudding noise, coming closer-a sound of many feet passing over the ground.

“What’s that?” Danny’s voice rose in a quaver.

A herd of ghostly, delicate animals appeared and wandered past the camp. They were daddy longlegs, also called harvestmen, eight-legged creatures walking on spindly legs that seemed impossibly long. From the point of view of the students, the legs spanned fifteen feet. The body of each daddy longlegs was an oval nugget perched on the legs, and the body sported two bright eyes. The creatures glided over the terrain, tapping their legs around, looking for things to eat.

“Giant spiders,” Danny hissed through his teeth.

“They’re not spiders,” Karen King said to him. “They’re Opiliones.”

“Meaning what?”

“They’re a cousin of spiders. They’re harmless.”

“Daddy longlegs are poisonous,” Danny said.

“No they aren’t!” Karen snapped at him. “They have no venom. Most of them eat fungus and decaying material, detritus. I think daddy longlegs are beautiful. To me, they’re the giraffes of the micro-world.”

“Only an arachnologist would say that,” Rick Hutter said to her.

The herd of daddy longlegs moved on, and the noises of their pattering feet faded. The darkness thickened and filled the forest like a rising tide. The sounds of the forest became different. It meant that a whole new set of creatures was coming out.

“It’s the changing of the guard,” Karen King’s voice came out of dimness. “The new shift will be hungry.” They couldn’t see one another clearly, now.

As the night advanced, the noises rose up and grew stronger, more insistent, swirling around them. From near and far came screeching, booming, wailing, tapping, whistling, stretched-out, growling, and pulsing sounds. The humans could feel vibrations running through the ground, too, for some insects communicated by tapping on the ground or on a surface. The students couldn’t understand a word of it.

They curled up next to one another, while Amar Singh took the first watch. Holding the harpoon, he climbed up on the leaf-roof of the fort, where he sat bolt upright, listening, and sniffing the air. The air was thick with pheromones. “I don’t know what I’m smelling,” he confessed. “It’s all strange to me.”

Amar began to wonder how they were able to smell anything. Their bodies had been shrunken by a factor of a hundred. Presumably this meant that the atoms in their bodies were a hundred times smaller, as well. If so, how could the tiny atoms in their bodies interact with the giant atoms of the environment? They shouldn’t be able to smell anything. In fact, they shouldn’t be able to taste anything. In fact, how could they breathe? How could the tiny hemoglobin molecules in their red blood cells capture the giant oxygen molecules that existed in the air they breathed? “There’s a paradox,” Amar said to the others. “How can the tiny atoms in our bodies interact with the normal-size atoms of the world around us? How can we smell anything? How can we taste anything? In fact, how does our blood manage to hold oxygen? We should be dead.”

No one could figure it out. “Maybe Kinsky would have had an answer,” Rick said.

“Maybe not,” Peter said. “I get the idea Nanigen doesn’t understand their own technology very well.”

Rick had been thinking about the micro-bends. He had been secretly inspecting his arms and hands, looking for bruises. So far he hadn’t noticed anything. “Maybe the micro-bends are caused by some mismatch in the sizes of atoms,” he said. “Maybe something goes wrong in the interactions between the small atoms in our bodies and the large atoms around us.”

A mite crawled over Amar, and he plucked it off his shirt and dropped it, not wanting to hurt the creature. “What about our gut bacteria? We have trillions of gut bacteria inside us. Did they get shrunk, too?”

Nobody had any idea.

Amar went on, “What happens if our super-tiny bacteria get loose in this ecosystem?”

“Maybe they’ll die of the bends,” Rick said.

A silvery glow had brightened the forest slightly. The moon was up, and was climbing higher in the sky. Along with the moon came an eerie, booming cry, which echoed through the forest: Puuu…eee…ooo…o-o-o-…

“My God, what was that?” someone said.

“I think it’s an owl. We’re hearing it at a lower frequency.”

The hoot sounded again, coming from a tree top, and the cry sounded like a death threat wrapped in a moan. They felt the owl’s lethal presence somewhere above them.

“I’m beginning to understand what it feels like to be a mouse,” Erika said. The hooting stopped, and then a pair of sinister wings crossed the canopy in total silence. The owl had bigger prey to catch; it had no interest in anything as small as a micro-human.

A creaking, rustling tremor shook them. The ground heaved.

“There’s something under us!” Danny cried, leaping to his feet. He lost his balance as the ground began to break apart and he began staggering back and forth as if on the deck of a heaving ship.

The others scrambled up off the bed of leaves, pulling out their machetes, while the earth under them groaned and trembled. Amar took up the harpoon, raised it over his head, his heart hammering in his chest. He was ready to kill. He knew it. The humans scattered, running up against the palisade, wondering if they should flee outside or wait and see the threat materialize.

And then it appeared, a pinkish-brown cylinder of stunning size, rising up from the bowels of the earth, thrusting the dirt before it. Danny screamed. Amar almost threw the harpoon, but checked the thrust at the last moment.

“It’s just an earthworm, guys,” Amar said, putting down the harpoon. He wasn’t going to stab an earthworm if he could help it; the gentle animal was just trying to make a living in the dirt, and was a threat to nobody.

The earthworm didn’t like what it found. It withdrew, sliding back down into the earth, and it traveled on, crunching like a bulldozer, while the palisade wall jiggled and shook.

As the moon climbed, the bats came out. The students began to hear whistling cries, staccato sounds, and whooshing roars, crisscrossing the treetops and gulfs above them: the bats’ sonar. The noise was eerie, the sound of flying predators using beams of ultrasound to probe the air for prey. A bat’s sonar is too high-pitched for human hearing. But in the micro-world, the bats sounded like submarines pinging the deep.

They heard a bat zeroing in on a moth and killing it.

The kill began with a lazy chain of pings. The bat was directing pulses of sound toward a moth, identifying the prey and ranging the moth, getting its distance and the direction it was flying. Next, the bat’s pings sped up and grew louder. Erika Moll explained what was happening. “The bat is ‘painting’ the moth with sonar. It is firing a beam of ultrasound at the moth and hearing the echoes that come back. The echoes tell the moth’s location, its size and shape, and the direction it’s flying. The pings get faster as the bat zeroes in on the moth.”

Often, as a bat was pinging a moth, the moth would defend itself with a loud drumming noise. “Moths have very good hearing,” Erika explained. The moth had heard the bat’s sonar, and the moth was starting up its defensive noisemakers. The banging sounds were coming from drums on the moth’s abdomen. The sounds could jam the bat’s sonar, confusing the bat, making the moth invisible to the bat. As a bat closed in on a moth, there would be a crescendo of bat pings, mixed with a rising drumming sound as the moth tried to jam the bat’s sonar. Ping, ping, ping, went a bat. Pom-pom-pom-pom, went a moth, trying to jam the bat’s sonar. Sometimes a moth’s drumming would end abruptly. “The bat ate the moth,” Erika informed them.