Mark Willis with moth
Flies, like airplanes, have gyroscopes to control their flight patterns. Now a collaborative group of researchers from Case Western Reserve University and the University of Washington have found for the first time that a moth's antennae can act like an airplane's gyroscope to stabilize its flight.
Sanjay Sane, a biologist from the University of Washington and lead author of this week's Science article, "Antennal Mechanosensors Mediate Flight Control in Moths," collaborated with Case biologist Mark Willis, in studying the large moth Manduca sexta (tobacco hornworm moth) to unravel how it controls it flight in an effort to build a new generation of flying robots.
"We are really good at building gyros for a 747 airplane, but if we want to make autonomous flying machines the size of a bird or smaller, we will need to engineer a version of the vibrating antennae. This information has the potential to help us design gyro-like stabilization capabilities for a small flying robot," said Willis.
While studying how moths use their antennae to sense smell, Willis noticed that when antennae were clipped or damaged, the moths struggled to maintain stable flight and would crash into walls, fly backwards or waver off course. If a severed antenna was reattached with Super Glue, the moth was able to regain flight control.
"This observation really emphasized to us that the antennae are more than just the moth's sense of smell," said Willis.
When placed under a microscope, a moth's antenna looks like a string of beads. Most of this "string" is covered with hair-like odor detectors used for locating food and mates. The joint where the antenna attaches to the moth's head is very flexible and has special touch sensors that control the position of the antenna and tell the brain about antennal movements. When the moth is flying, its body bobs up and down with each wing beat, just like humans do when we walk. The touch sensors at the base of each antenna report this regular bobbing to the brain. This regular signal changes when the moth encounters in-flight turbulence that could send the moth off course. When this happens the moth makes a course correction and stabilizes its flight pattern.
Touch sensors are particularly important for the moth since it flies in low light conditions at night, when processing visual information in these conditions is much slower than touch. Fast flying insects need to know as soon as possible if they are veering of course to avoid crashing, according to Willis.
Members of the University of Washington's team have experience studying how insects from the Dipteran family, like the common house, fly stabilize their flight. Flies have specialized structures called halteres behind their wings. These fly gyroscopes beat at their wing-beat frequency (approximately 100 times per second) and also have special touch sensors that sense changes in flight. The halteres constantly send messages through neurons to change flight muscles and wing motion to alter where the fly goes.
Until University of Washington-Case group collaborated, flies were the only insect known to have a built-in gyroscope to control flight.
It is really the unique array of skills and experience with insect flight assembled in this collaboration between the workers at UW and Case that made this discovery happen. "Working with Sanjay, Alexandre and Tom is really fun," says Willis. His collaboration with the lab of Tom Daniel (also an author on the paper) at the University of Washington is funded by an Office of Naval Research multi-university research initiative (MURI grant).
In addition to the Office of Naval Research grant, the research has the support from the National Science Foundation Inter-Disciplinary Informatics Grant to Sane. Also collaborating on the Science article was University of Washington biologist Alexandre Dieudonne.
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