Fly behavior could enable drones to find chemical leaks
In an on-line paper, University of Nevada, Reno Assistant Professor Floris van Breugel and Postdoctoral Researcher S. David Stupski have determined why flies buzz around in circles when the air is still. The answer to this behaviour could hold a key to public safety — specifically, how to better train robots and drones to track chemical leaks.
“We don’t currently have robotic systems to track odor or chemical plumes,” van Breugel said. “We don’t know how to efficiently find the source of a wind-borne chemical. But insects are remarkably good at tracking chemical plumes, and if we really understood how they do it, maybe we could train inexpensive drones to use a similar process to find the source of chemicals and chemical leaks.”
A fundamental challenge in understanding how insects track chemical plumes is that wind and odours can’t be independently manipulated.
To address this challenge, van Breugel and Stupski used a new approach that makes it possible to remotely control neurons — specifically the “smell” neurons — on the antennae of flying fruit flies by genetically introducing light-sensitive proteins, an approach called optogenetics. These experiments, part of a $450,000 project funded through the Air Force Office of Scientific Research, made it possible to give flies identical virtual smell experiences in different wind conditions.
The experiments were designed to answer how flies find an odour when there’s no wind to carry it? This is, after all, likely the wind experience of a fly looking for a banana in a kitchen.
Flies use environmental cues to detect and respond to air currents and wind direction to find their food sources, according to van Breugel. In the presence of wind, those cues trigger an automatic “cast and surge” behavior, in which the fly surges into the wind after encountering a chemical plume (indicating food) and then casts — moves side to side — when it loses the scent. Cast-and-surge behavior long has been understood by scientists but, according to van Breugel, it was fundamentally unknown how insects searched for a scent in still air.
Through their work, van Breugel and Stupski uncovered another automatic behaviour, sink and circle, which involves lowering altitude and repetitive, rapid turns in a consistent direction. Flies perform this innate movement consistently and repetitively, even more so than cast-and-surge behaviour.
According to van Breugel, the most exciting aspect of this discovery is that it shows flying flies are clearly able to assess the conditions of the wind — its presence, and direction — before deploying a strategy that works well under these conditions. Flies aren’t just reacting to an odour with the same preprogrammed response every time like a simple robot, they are responding in context-appropriate manner. This knowledge potentially could be applied to train more sophisticated algorithms for scent-detecting drones to find the source of chemical leaks.
Image: Assistant Professor Floris van Breugel and postdoctoral researcher David Stupski have uncovered an automatic behavior in flies, sink and circle, which involves lowering altitude and repetitive, rapid turns in a consistent direction. It shows that flying flies are able to assess the conditions of the wind before deploying a strategy to find a odor (which leads to a food source) using a strategy that will work well under those conditions. Flies aren’t just reacting to an odor with a preprogrammed response: they are responding in context-appropriate manner. This knowledge potentially could be applied to train more sophisticated algorithms for scent-detecting drones to find chemical leaks. Credit: Chris Moran.
Paper: “Wind Gates Olfaction Driven Search States in Free Flight” — DOI: https://doi.org/10.1016/j.cub.2024.07.009.
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