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A new research sheds light on how small fly navigate through difficult situations


The Gnat Ogre is a small predator that catches other insects out of the air with pinpoint accuracy. New study demonstrates how nature-inspired ideas work and how they can affect future breakthroughs.

It’s difficult to image a creature with a brain smaller than the period at the end of this sentence successfully navigating around obstacles while following fast-moving prey on the wing, especially for those of us who periodically trip over a curb or bump into a door frame. Researchers from the University of Minnesota and Imperial College London published a new study in the Journal of Experimental Biology that demonstrates how a small fly can accomplish precisely that, providing vital insights for attempts to create robots, drones, and other devices.

The study, led by Paloma Gonzalez-Bellido, Mary Sumner, and Trevor Wardill of the University of Minnesota’s College of Biological Sciences and Sam Fabian of Imperial College London’s Department of Bioengineering, focuses on the aerial feats of a miniature robber fly known as a gnat ogre — adults are only 7 mm long on average. The gnat ogre, which is native to North and South America, is recognized for its extraordinary accuracy in pursuing and capturing other insects in flight. It’s impressive enough that this insect’s small brain can direct it to capture a moving item. Even more impressive is its ability to avoid colliding with objects at the same time. The scientists wanted to know how the small fly mixes the two sets of brain-to-muscle commands.

“Predatory lifestyles place a premium on neurological ability to move swiftly and accurately, and this strain is amplified in small animals because they have fewer neurons,” said Gonzalez-Bellido, the director of the University of Minnesota’s Fly Systems Laboratory (FLYSY). “However, Gnat ogres intercept their prey, much like a football player collecting an over-the-shoulder pass, so we wanted to see how adaptable their method is and whether these flies could deal with extra problems during the interception, such as impediments in their route.”

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They looked for an explanation by monitoring gnat ogres chasing a moving object with the use of plastic bait, fishing line, and high-speed video. The researchers discovered that gnat ogres continuously adjusted their path based on a mix of visual stimuli when comparing video recordings of the fly chasing the bait in the presence of obstacles with flight trajectories predicted by models of obstacle-eluding flight and moving-object-pursuing flight. The bug was likely to cease the hunt if the obstruction was substantial enough to conceal the prey for more than 70 milliseconds. The pursuit continued after the fly passed the obstruction, even though the line of sight was scarcely broken.

“We found that basic visual input alone may be utilized to efficiently tackle difficult navigation issues,” adds Fabian, who earned his Ph.D. in the FLYSY Lab. “This research demonstrates that even species with relatively little brains are capable of extraordinary and precise behavior at speeds humans can barely perceive, much alone appreciate.”

The ability of the fly to change its direction so quickly is attributed to its tiny size, which enables signals to flow quickly from the eye to the brain to the flying muscles. Future studies will look at how tiny animals get information about their target before taking off and how they know what to attack. The results might have ramifications in other disciplines that are looking at nature-inspired innovation.

“To perform tasks such as obstacle avoidance, current robots technology tends to employ additional, costly sensors (e.g. LIDAR or RADAR). Animals like our robber flies, on the other hand, can perform numerous tasks at once utilizing just input from their visual system (e.g., following the movements of a distant target and analyzing the location and expansion of possible impediments) and on a very limited energy budget “explains Fabian. “Understanding how they use this sensory information to develop precise and quick behavioral responses to challenging navigational obstacles might drive future robotic sensing capabilities innovation.”

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The US Air Force Office of Scientific Research, the Isaac Newton Trust, the Wellcome Trust, the University of Cambridge, the Biotechnology and Biological Sciences Research Council, and Imperial College London all contributed to this study.

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