What do bumblebees and drones have in common? Besides the ability to fly, not much at first glance. There’s more to bees than meets the eye though, and studying how they fly in their natural habitat can help us build the drones of the future. Despite only seeing blurry images, bumblebees are able to navigate through forests or cities with ease and avoid obstacles in their way. This is the sort of natural flight path we want drones to be capable of, but first we have to understand just how insects do it. Nellie Linander didn’t set out to study insect flight control, but the PhD position was available at Lund University and she had always been interested in insects. Inspired by British naturalist David Attenborough, her goal was to learn as much as possible about these little critters and master new tools and techniques along the way. Now, PhD in hand, Nellie’s research has deepened our understanding of how bumblebees use their limited vision to control their flight.
Although their brains are proportionally smaller than birds’, bumblebees are able to fly at speeds of 25km per hour through complex environments (like your picnic) without crashing into things. They navigate by using information about optic flow, the pattern of image motion information generated on their retinas as they fly through an environment. You’ve experienced optic flow yourself if you’ve ever looked out the window of a fast-moving car or train. The landscape appears to be moving backwards, which tells you that you are moving forward at a high speed. Optic flow also tells you how far away things are. When you’re looking out the window the objects that are closer to you, like trees or road signs, appear to move faster than objects in the distance, like clouds or mountains. Insects rely on this same information when they are flying. By measuring the rate of optic flow insects can estimate how fast they are flying, how far off the ground they are, and the distance to nearby objects.
The best place for insects to measure optic flow is laterally at 90° (right out of the corners of their eyes) where the optic flow effect is the greatest. However, when a bee is flying through something dense like a forest, it is not effective for them to only measure optic flow laterally because then they would constantly be crashing into obstacles right in front of them. So why doesn’t this happen? This is one of the key questions for Nellie’s research. She filmed bumblebees flying through a set of tunnels of varying width and complexity and then analysed their flight patterns. She found that bumblebees don’t just measure optic flow laterally, they measure optic flow wherever it is greatest in their frontal visual field (i.e. directly in front of them). This flexibility allows them to detect changes in the environment before they reach them as well as fly safely at high speeds. Furthermore, Nellie found that the exact place insects measure optic flow in the visual field changes based on the type of environment they are flying through. When insects fly through narrow spaces they control their flight by using lateral optic flow information, whereas they use optic flow information from the ground when flying in wide open spaces.
Understanding how bees use optic flow information to control their flight patterns can help engineers develop more efficient drones. Using optic flow information like the bees do could help drones estimate distances better, especially when landing. Eventually optic flow research could be used to develop bee-inspired autopilot system to guide drones around unexpected twists and turns. Another reason to save the bees!