They were definitely swarming.
"Swarming" was a term for the behavior of certain social insects like ants or bees, which swarmed whenever the hive moved to a new site. A cloud of bees will fly in one direction and then another, forming a dark river in the air. The swarm might halt and cling to a tree for perhaps an hour, perhaps overnight, before continuing onward. Eventually the bees settled on a new location for their hive, and stopped swarming.
In recent years, programmers had written programs that modeled this insect behavior. Swarm-intelligence algorithms had become an important tool in computer programming. To programmers, a swarm meant a population of computer agents that acted together to solve a problem by distributed intelligence. Swarming became a popular way to organize agents to work together. There were professional organizations and conferences devoted entirely to swarm-intelligence programs. Lately it had become a kind of default solution-if you couldn't code anything more inventive, you made your agents swarm.
But as I watched, I could see this cloud was not swarming in any ordinary sense. The sinuous back-and-forth motion seemed to be only part of its movement. There was also a rhythmic expansion and contraction, a pulse, almost like breathing. And intermittently, the cloud seemed to thin out, and rise higher, then to collapse down, and become more squat. These changes occurred continuously, but in a repeating rhythm-or rather a series of superimposed rhythms. "Shit," Ricky said. "I don't see the others. And I know it's not alone." He pressed the radio again. "Vince? You see any others?"
"No, Ricky."
"Where are the others? Guys? Speak to me."
Radios crackled all over the facility. Bobby Lembeck: "Ricky, it's alone."
"It can't be alone."
Mae Chang: "Ricky, nothing else is registering out there."
"Just one swarm, Ricky." That was David Brooks.
"It can't be alone!" Ricky was gripping the radio so tightly his fingers were white. He pressed the button. "Vince? Take the PPI up to seven."
"You sure?"
"Do it."
"Well, all right, if you really think-"
"Just skip the fucking commentary, and do it!"
Ricky was talking about increasing the positive pressure inside the building to seven pounds per square inch. All clean facilities maintained a positive pressure so that outside dust particles could not enter from any leak; they would be blown outward by the escaping air. But one or two pounds was enough to maintain that. Seven pounds of positive pressure was a lot. It was unnecessary to keep out passive particles.
But of course these particles weren't passive.
Watching the cloud swirl and undulate as it came closer, I saw that parts of it occasionally caught the sunlight in a way that turned it a shimmering, iridescent silver. Then the color faded, and the swarm became black again. That had to be the piezo panels catching the sun. But it clearly demonstrated that the individual microunits were highly mobile, since the entire cloud never turned silver at the same time, but only portions, or bands. "I thought you said the Pentagon was giving up on you, because you couldn't control this swarm in wind."
"Right. We couldn't."
"But you must have had strong wind in the last few days."
"Of course. Usually comes up in late afternoon. We had ten knots yesterday."
"Why wasn't the swarm blown away?"
"Because it's figured that one out," Ricky said gloomily. "It's adapted to it."
"How?"
"Keep watching, you'll probably see it. Whenever the wind gusts, the swarm sinks, hangs near the ground. Then it rises up again once the wind dies down."
"This is emergent behavior?"
"Right. Nobody programmed it." He bit his lip. Was he lying again?
"So you're telling me it's learned…"
"Right, right."
"How can it learn? The agents have no memory."
"Uh… well, that's a long story," Ricky said.
"They have memory?"
"Yes, they have memory. Limited. We built it in." Ricky pressed the button on his radio. "Anybody hear anything?"
The answers came back, crackling in his handset.
"Not yet."
"Nothing."
"No sounds?"
"Not yet."
I said to Ricky, "It makes sounds?"
"We're not sure. Sometimes it seems like it. We've been trying to record it…" He flicked keys on the workstation, quickly shifting the monitor images, making them larger, one after another. He shook his head. "I don't like this. That thing can't be alone," he said. "I want to know where the others are."
"How do you know there are others?"
"Because there always are." He chewed his lip tensely as he looked at the monitor. "I wonder what it's up to now…"
We didn't have long to wait. In a few moments, the black swarm had come within a few yards of the building. Abruptly, it divided in two, and then divided again. Now there were three swarms, swirling side by side.
"Son of a bitch," Ricky said. "It was hiding the others inside itself." He pushed his button again. "Guys, we got all three. And they're close."
They were, in fact, too close to be seen by the ground-view camera. Ricky switched to the overhead views. I saw three black clouds, all moving laterally along the side of the building. The behavior seemed distinctly purposeful.
"What're they trying to do?" I said.
"Get inside," Ricky said.
"Why?"
"You'd have to ask them. But yesterday one of them-"
Suddenly, from a clump of cactus near the building, a cottontail rabbit sprinted away across the desert floor. Immediately, the three swarms turned and pursued it. Ricky switched the monitor view. We now watched at ground level. The three clouds converged on the terrified bunny, which was moving fast, a whitish blur on the screen. The clouds swirled after it with surprising speed. The behavior was clear: they were hunting. I felt a moment of irrational pride. PREDPREY was working perfectly! Those swarms might as well be lionesses chasing a gazelle, so purposeful was their behavior. The swarms turned sharply, then split up, cutting off the rabbit's escape to the left and right. The behavior of the three clouds clearly appeared coordinated. Now they were closing in. And suddenly one of the swarms sank down, engulfing the rabbit. The other two swarms fell on it moments later. The resulting particle cloud was so dense, it was hard to see the rabbit anymore. Apparently it had flipped onto its back, because I saw its hind legs kicking spasmodically in the air, above the cloud itself.
I said, "They're killing it…"
"Yeah," Ricky said, nodding. "That's right."
"I thought this was a camera swarm."
"Yeah, well."
"How are they killing it?"
"We don't know, Jack. But it's fast."
I frowned. "So you've seen this before?"
Ricky hesitated, bit his lip. Didn't answer me, just stared at the screen.
I said, "Ricky, you've seen this before?"
He gave a long sigh. "Yeah. Well, the first time was yesterday. They killed a rattlesnake yesterday."
I thought, they killed a rattlesnake yesterday. I said, "Jesus, Ricky." I thought of the men in the helicopter, talking about all the dead animals. I wondered if Ricky was telling me all he knew.
"Yeah."
The rabbit no longer kicked. A single protruding foot trembled with small convulsions, and then was still. The cloud swirled low to the ground around the animal, rising and falling slightly. This continued for almost a minute.
I said, "What're they doing now?"