Flies could inspire scent-detecting drones that sniff chemical leaks

Researchers have found an answer to the phenomenon of flies buzzing around in circles when the air is still and why it matters.

A team at the University of Nevada’s work could hold a key to public safety—specifically, how to better train robotic systems to track chemical leaks.

While exclusively talking to Interesting Engineering , Floris van Breugel, Reno Assistant Professor at the institution, explained this phenomenon.

Flies use environmental cues to detect and respond to air currents and wind direction to find food. In windy conditions, they exhibit a “cast and surge” behavior—surging into the wind after detecting a chemical plume and moving side to side when the scent is lost.

They also discovered another automatic behavior called “sink and circle,” where flies lower their altitude and make rapid, repetitive turns in a consistent direction. This behavior is even more consistent and repetitive than cast-and-surge.

The details of the team’s study were published in the journal Current Biology .

Drosophila’s search strategies

The velocity of the fluid surrounding an organism is crucial for its success when following a chemical trail to its source. When engaged in an olfactory-driven search, swimming and flying animals often begin by orienting themselves towards an approaching wind or water current.

However, it is unknown how organisms modify their strategies when directional cues are absent or inconsistent, as is often the case in nature.

Using Drosophila melanogaster’s genetic toolkit, the team developed an optogenetic method to simulate precise “virtual” olfactory experiences for free-flying flies in wind or still air.

In the wind, flies quickly turn upwind within about 100 ms, indicating they estimate wind direction before moving upwind. In still air, flies use a “sink and circle” search pattern, making consistent 60-degree turns at 3–4 Hz.

Researchers say the findings demonstrate that Drosophila assesses wind presence and direction before choosing a search strategy. In both wind and still air, flies decelerate and perform rapid turns right after detecting an odor.

These behaviors align with theoretical predictions on how insects gauge wind properties during flight, suggesting flies actively sense their wind environment before starting their search.

“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,” said Breugel in a statement .

Adapting plume tracking

Thus far, the development of robotic systems for monitoring plumes has primarily relied on the concept of cast and surge, which is shared by all plume-tracking species.

The team’s research demonstrates that in still air, animals (in this case, flies , but researchers assume others do this as well) will employ a different tactic.

“So if one were to make a robotic system designed to track chemical plumes you would probably want it to do some kind of cast-surge behavior outdoors in the wind, but if it got to a building and went inside where the air was relatively still, switching to a sink and circle behavior might be a good idea,” Breugel told Interesting Engineering.

Estimating wind direction is challenging for both flies and drones. The research team’s hypothesis suggests that flies might resolve this difficulty by changing direction and slowing down, a strategy that could also benefit drones. They recommend that drones adopt this approach to improve wind direction estimation. The team is currently working on developing this method.

As limitations go, the main challenges in developing practical sensors lie in their sensitivity and size. Flies have incredibly small yet highly sensitive systems for detecting chemicals and airflow.

Researchers are working on bio-inspired and bio-hybrid systems to improve current sensors . One approach involves using a moth’s antennae for chemical detection in drones. Another study looked at developing small-scale insect-inspired airflow sensors.