WRIGHT-PATTERSON AIR FORCE BASE, Ohio — Two miles from the cow pasture where the Wright Brothers learned to fly the first airplanes, military researchers are at work on another revolution in the air: shrinking unmanned drones, the kind that fire missiles into Pakistan and spy on insurgents in Afghanistan, to the size of insects and birds.

The base’s indoor flight lab is called the “microaviary,” and for good reason. The drones in development here are designed to replicate the flight mechanics of moths, hawks and other inhabitants of the natural world. “We’re looking at how you hide in plain sight,” said Greg Parker, an aerospace engineer, as he held up a prototype of a mechanical hawk that in the future might carry out espionage or kill.

Half a world away in Afghanistan, Marines marvel at one of the new blimplike spy balloons that float from a tether 15,000 feet above one of the bloodiest outposts of the war, Sangin in Helmand Province. The balloon, called an aerostat, can transmit live video — from as far as 20 miles away — of insurgents planting homemade bombs. “It’s been a game-changer for me,” Capt. Nickoli Johnson said in Sangin this spring. “I want a bunch more put in.”

From blimps to bugs, an explosion in aerial drones is transforming the way America fights and thinks about its wars. Predator drones, the Cessna-sized workhorses that have dominated unmanned flight since the Sept. 11, 2001, attacks, are by now a brand name, known and feared around the world. But far less known is the sheer size, variety and audaciousness of a rapidly expanding drone universe, along with the dilemmas that come with it.