Vanessa Alarcon saw them while working at an antiwar rally in Lafayette Square last month.
"I heard someone say, 'Oh my god, look at those,' " the college senior from New York recalled. "I look up and I'm like, 'What the hell is that?' They looked kind of like dragonflies or little helicopters. But I mean, those are not insects."
Out in the crowd, Bernard Crane saw them, too.
"I'd never seen anything like it in my life," the Washington lawyer said. "They were large for dragonflies. I thought, 'Is that mechanical, or is that alive?' "
That is just one of the questions hovering over a handful of similar sightings at political events in Washington and New York. Some suspect the insectlike drones are high-tech surveillance tools, perhaps deployed by the Department of Homeland Security.
Others think they are, well, dragonflies -- an ancient order of insects that even biologists concede look about as robotic as a living creature can look.
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No agency admits to having deployed insect-size spy drones. But a number of U.S. government and private entities acknowledge they are trying. Some federally funded teams are even growing live insects with computer chips in them, with the goal of mounting spyware on their bodies and controlling their flight muscles remotely.
The robobugs could follow suspects, guide missiles to targets or navigate the crannies of collapsed buildings to find survivors.
The technical challenges of creating robotic insects are daunting, and most experts doubt that fully working models exist yet.
"If you find something, let me know," said Gary Anderson of the Defense Department's Rapid Reaction Technology Office.
But the CIA secretly developed a simple dragonfly snooper as long ago as the 1970s. And given recent advances, even skeptics say there is always a chance that some agency has quietly managed to make something operational.
"America can be pretty sneaky," said Tom Ehrhard, a retired Air Force colonel and expert in unmanned aerial vehicles who is now at the Center for Strategic and Budgetary Assessments, a nonprofit Washington-based research institute.
Robotic fliers have been used by the military since World War II, but in the past decade their numbers and level of sophistication have increased enormously. Defense Department documents describe nearly 100 different models in use today, some as tiny as birds, and some the size of small planes.
All told, the nation's fleet of flying robots logged more than 160,000 flight hours last year -- a more than fourfold increase since 2003. A recent report by the U.S. Army Command and General Staff College warned that if traffic rules are not clarified soon, the glut of unmanned vehicles "could render military airspace chaotic and potentially dangerous."
But getting from bird size to bug size is not a simple matter of making everything smaller.
"You can't make a conventional robot of metal and ball bearings and just shrink the design down," said Ronald Fearing, a roboticist at the University of California at Berkeley. For one thing, the rules of aerodynamics change at very tiny scales and require wings that flap in precise ways -- a huge engineering challenge.
Only recently have scientists come to understand how insects fly -- a biomechanical feat that, despite the evidence before scientists' eyes, was for decades deemed "theoretically impossible." Just last month, researchers at Cornell University published a physics paper clarifying how dragonflies adjust the relative motions of their front and rear wings to save energy while hovering.
That kind of finding is important to roboticists because flapping fliers tend to be energy hogs, and batteries are heavy.
The CIA was among the earliest to tackle the problem. The "insectothopter," developed by the agency's Office of Research and Development 30 years ago, looked just like a dragonfly and contained a tiny gasoline engine to make the four wings flap. It flew but was ultimately declared a failure because it could not handle crosswinds.
Agency spokesman George Little said he could not talk about what the CIA may have done since then. The Office of the Director of National Intelligence, the Department of Homeland Security and the Secret Service also declined to discuss the topic.
Only the FBI offered a declarative denial. "We don't have anything like that," a spokesman said.
The Defense Department is trying, though.
In one approach, researchers funded by the Defense Advanced Research Projects Agency (DARPA) are inserting computer chips into moth pupae -- the intermediate stage between a caterpillar and a flying adult -- and hatching them into healthy "cyborg moths."
The Hybrid Insect Micro-Electro-Mechanical Systems project aims to create literal shutterbugs -- camera-toting insects whose nerves have grown into their internal silicon chip so that wranglers can control their activities. DARPA researchers are also raising cyborg beetles with power for various instruments to be generated by their muscles.
"You might recall that Gandalf the friendly wizard in the recent classic 'Lord of the Rings' used a moth to call in air support," DARPA program manager Amit Lal said at a symposium in August. Today, he said, "this science fiction vision is within the realm of reality."
A DARPA spokeswoman denied a reporter's request to interview Lal or others on the project.
The cyborg insect project has its share of doubters.
"I'll be seriously dead before that program deploys," said vice admiral Joe Dyer, former commander of the Naval Air Systems Command, now at iRobot in Burlington, Mass., which makes household and military robots.
By contrast, fully mechanical micro-fliers are advancing quickly.
Researchers at the California Institute of Technology have made a "microbat ornithopter" that flies freely and fits in the palm of one's hand. A Vanderbilt University team has made a similar device.
With their sail-like wings, neither of those would be mistaken for insects. In July, however, a Harvard University team got a truly fly-like robot airborne, its synthetic wings buzzing at 120 beats per second.
"It showed that we can manufacture the articulated, high-speed structures that you need to re-create the complex wing motions that insects produce," said team leader Robert Wood.
The fly's vanishingly thin materials were machined with lasers, then folded into three-dimensional form "like a micro-origami," he said. Alternating electric fields make the wings flap. The whole thing weighs just 65 milligrams, or a little more than the plastic head of a push pin.
Still, it can fly only while attached to a threadlike tether that supplies power, evidence that significant hurdles remain.
In August, at the International Symposium on Flying Insects and Robots, held in Switzerland, Japanese researchers introduced radio-controlled fliers with four-inch wingspans that resemble hawk moths. Those who watch them fly, its creator wrote in the program, "feel something of 'living souls.' "
Others, taking a tip from the CIA, are making fliers that run on chemical fuels instead of batteries. The "entomopter," in early stages of development at the Georgia Institute of Technology and resembling a toy plane more than a bug, converts liquid fuel into a hot gas, which powers four flapping wings and ancillary equipment.
"You can get more energy out of a drop of gasoline than out of a battery the size of a drop of gasoline," said team leader Robert Michelson.
Even if the technical hurdles are overcome, insect-size fliers will always be risky investments.
"They can get eaten by a bird, they can get caught in a spider web," said Fearing of Berkeley. "No matter how smart you are -- you can put a Pentium in there -- if a bird comes at you at 30 miles per hour there's nothing you can do about it."
Protesters might even nab one with a net -- one of many reasons why Ehrhard, the former Air Force colonel, and other experts said they doubted that the hovering bugs spotted in Washington were spies.
So what was seen by Crane, Alarcon and a handful of others at the D.C. march -- and as far back as 2004, during the Republican National Convention in New York, when one observant but perhaps paranoid peace-march participant described on the Web "a jet-black dragonfly hovering about 10 feet off the ground, precisely in the middle of 7th avenue . . . watching us"?
They probably saw dragonflies, said Jerry Louton, an entomologist at the National Museum of Natural History. Washington is home to some large, spectacularly adorned dragonflies that "can knock your socks off," he said.
At the same time, he added, some details do not make sense. Three people at the D.C. event independently described a row of spheres, the size of small berries, attached along the tails of the big dragonflies -- an accoutrement that Louton could not explain. And all reported seeing at least three maneuvering in unison.
"Dragonflies never fly in a pack," he said.
Mara Verheyden-Hilliard of the Partnership for Civil Justice said her group is investigating witness reports and has filed Freedom of Information Act requests with several federal agencies. If such devices are being used to spy on political activists, she said, "it would be a significant violation of people's civil rights."
For many roboticists still struggling to get off the ground, however, that concern -- and their technology's potential role -- seems superfluous.
"I don't want people to get paranoid, but what can I say?" Fearing said. "Cellphone cameras are already everywhere. It's not that much different."