CWRU researchers help Air Force think small—as in bug size

Flies and moths can hover, maneuver and fly to a target through a moonless night better than any manmade aircraft. Biologists at Case Western Reserve University are helping the U.S. Air Force to understand how.

The military wants to build flying machines no bigger than the size of a large moth for search and rescue missions, to detect mines or survey damaged buildings, to spy and more.

Headshot of Jessica Fox
Jessica Fox

Faculty at Case Western Reserve are studying the insect versions of gyroscopes and flight controls as members of the Air Force Center of Excellence on Nature-Inspired Flight Technologies and Ideas based at the University of Washington.

“We’re looking at biology to learn how to build sensors for flying robots,” said Jessica Fox, assistant professor of biology at Case Western Reserve.

“Flies have had about 200 million years to evolve flight mechanisms. They’re fast, stable and incredibly maneuverable,” she said. “If we could make things that fly like flies, that would be incredible.”

Mark Willis
Mark Willis

Fox, an expert in flies, and biology Professor Mark Willis, whose specialty is moths, will study how the insects maneuver and track food or potential mates, and how they can do so in complete darkness or other inhospitable conditions.

The researchers are focusing on the hindwings in moths and organs called halteres, which evolved from hindwings in flies.

Halteres resemble dumbbells and are used strictly for sensing. Sensors at the base of the dumbbells tell the fly the forces it’s feeling.

“Halteres act like little gyroscopes that tell the fly if its body is rotating,” Fox said. “We have inner ears to do that.”

Flight engineers are interested in how halteres work, Willis said, “because they perform just like manmade gyroscopes, but are much smaller and lighter.”

See Fox’s high-speed video showing a crane fly’s halteres oscillating just behind the wings during flight:

Other researchers have shown that sensors in moth wings are the same type of sensors associated with halteres and that, while moths can fly without their hindwings, they cannot maneuver well. Recently, Tom Daniel, a University of Washington biology professor and director of the center of excellence, demonstrated that moths use sensors in their wing veins to detect wind gusts and other changes in forces on their wings during flight, and steer to compensate for the disturbance.

But that’s about all that’s known about these sensory systems.

Fox and Willis have begun investigating how flies and moths use their wing and haltere sensors to encode body-rotating information and how their brains combine this information with sight, and how these inputs work together.

The biologists use high-speed video to study how files use halteres on the ground and when they take off. (Flies can’t take off without them.) And they’ll run experiments to determine if moths fly poorly without hindwings due to loss of aerodynamics or loss of sensors.

Their labs will record activities in the nerves and in the insect brains as the researchers stimulate halteres and hindwings, and as they stimulate their vision, sense of smell and more.

“Flies and moths orient to odors, navigating to a source some distance away,” Willis said. “That’s a complicated behavior.”

A tobacco hornworm moth, Manduca sexta
A tobacco hornworm moth, Manduca sexta, following a scent trail to a potential mate. Photo by Charles Hedgecock

He and Fox will model how insects take odor information and input from the halteres or hindwings, combine that with goal-directed behavior of finding a mate or food, and constantly integrate these changing flows of information to reach their targets.

“It’s hard to tell how their brains put this together dynamically—with each wing beat there’s more information and changing information,” Willis said.

But those are the capabilities the military seeks for such possible uses as building a quadrotor that tracks chemicals or radiation or some other target through treetops or cityscapes.

The center of excellence includes researchers from CWRU, University of Maryland, Johns Hopkins University and University of Washington, and is on course to receive up to $9 million in funding over six years from the Air Force Office of Scientific Research.