Insects were masters of the air when birds first got their wings more than 100 million years ago, and they’re still the go-to place for scientists interested in the evolution, kinematics, and neuroscience of flight. Today, engineers are developing drones and other biomimetic robots designed to mimic the way insects fly and respond to environmental stimuli such as smells, shapes, and magnetic fields.
Because insects are smaller and faster than many of their aerial counterparts such as birds and bats, many of the tools used to study these larger animals cannot be miniaturized to study insect flight. To address these challenges, researchers are getting more creative, aggregated technology from many different fields – including video games, robotics, radar, and even missile guidance systems – to better understand how insects became such successful fliers.
The difficulties in studying flight
Some larger insects, such as dragonflies and hawk moths, can be equipped with trackers and other devices to help study flight. Huai-Ti Lin, a neural engineer at Imperial College London, has developed an ultra-light backpack, pictured here, that uses electrodes implanted directly into a dragonfly’s brain to measure its neural activity in real time.
Many insects are simply too small to be equipped with a tracker. Instead, researchers use high-speed cameras that can capture thousands of images per second to study the flight and behavior of insects. To analyze so much footage, scientists turn to deep learning neural networks like DeepLabCut, which can be trained to track parts of an insect’s body as it moves.
DEEPLABCUT; DATA FROM LIN ET AL. 2017, DEEPLABCUT
Virtual reality arenas bring the field into the laboratory
Video game technology has enabled researchers to mimic field conditions in the laboratory or analyze the reality of an insect in ways that would never be possible in nature.
Shannon Alson; ANDREW STRAW
Virtual reality enables researchers to replicate realistic stimuli such as trees, fruits, and flowers. Shannon Olsson, a chemical ecologist at the Tata Institute for Basic Research in Bangalore, India, combines VR with olfactory plumes to record how tethered insects like apple flies, mosquitoes and moths navigate to virtual landmarks.
Neuroscientists at the University of Freiburg recently designed a virtual reality arena called FreemoVR, in which animals can navigate without being connected. To validate the arena, designer Andrew Straw asked Drosophila to fly in a figure eight by varying the speed and direction of the points displayed on the arena’s wraparound screen.
Lab-on cables follow insects through the air
Dominique Martinez, a neurobiologist at the University of Lorraine in France, started brainstorming how to follow insects in free flight in 2016. The resulting “lab-on-cables” resembles the spidercams that were used for filming in sports arenas. A rigid outer frame supports a series of winches and cables that control the position of a small central cube in which an insect is flying.
As the animal swims around, a tracking algorithm derived from missile guidance technology analyzes the footage from two cameras attached to the cube and uses the information to predict where the insect will fly next, tightening or loosening the cables around the insect inside the cube to keep. A third high-speed camera records up to 400 images per second and enables the researchers to examine the detailed kinematics of the flight. Here a long exposure captures the path of the cube following a previously recorded flight path using a small LED light attached to a corner.
The team validated the lab-on-cable by tracking free-flying cutworm moths (Agrotis ipsilon) and was able to show that moths have adapted a known type of flight, which is described by the so-called helicopter model – when moths fly relatively slowly, moths tend to do theirs To align the body vertically and to align itself horizontally when higher speeds are reached.
Use radar to track insects
While many countries have radar networks in place to predict the weather, their signals often also contain information about insects. Biometeorologists at Notre Dame University use radar to track the annual occurrence of mayflies around Lake Erie, where billions of adults emerge from the water every summer in a mating frenzy that lasts for days.
By analyzing radar data over the past five years, scientists have documented a decrease in mayfly frequency in more than 80 percent of Lake Erie. Mayflies are food for many different animals throughout their lives, and the Great Lakes fishing industry indirectly relies on their presence. Researchers attribute the decline in the mayfly population to industrial and agricultural contamination.
Scientists are also developing special entomological radars that can get more detailed information than the size, shape, speed, direction and orientation of individual insects than weather radar stations. In Australia, these radars are used by the government to monitor a common agricultural pest, the Australian pest locust (Chortoicetes terminifera).
ALISTAIR DRAKE; REG EADE, NEW SOUTH WALES LIVESTOCK HEALTH AND POLLUTION AUTHORITIES
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