Hawkmoths are able see in the dark, and now, researchers know how they do it. This ability allows them to track the movements of flowers blowing in the wind, even at night, as the insects hover in the air.
Manduca sexta, roughly the size of a hummingbird, were studied by researchers using infrared cameras as they traveled between mechanical flowers. As the team varied light conditions, they also altered the speed at which the artificial flowers swayed from side to side. They then recorded how well the proboscis (feeding probe) of the insects stayed within the target flower.
The moths are able to slow down their brains while seeking nectar, improving their eyesight under conditions of low visibility, the study found. While their minds are working on reduced speed, the creatures are also able to maintain rapid flapping of their wings and maintaining complex flight characteristics.
The mechanical flowers used in the study were created on 3D printers. Real flowers were studied in the wild to determine how much they moved from side to side, as well as typical velocities for the movements. Natural vegetation typically moved through no more than two oscillations a second, although investigators found they were capable of following speeds 10 times that rate.
Researchers believe this new investigation could help engineers to build a new generation of small aerial robots that could be used for surveillance, rescue operations or other purposes. The research was funded, in part, by the Air Force Office of Scientific Research.
"There has been a lot of interest in understanding how animals deal with challenging sensing environments, especially when they are also doing difficult tasks like hovering in mid-air. This is also a very significant challenge for micro air vehicles," said Simon Sponberg from the School of Physics and School of Applied Physiology at the Georgia Institute of Technology.
Biologists were already aware of several physical adaptations moths have evolved to optimize their vision in low-light conditions. Some researchers had theorized that the moths could slow down the actions of their nervous systems in order to improve night vision. However, biologists could not understand how the animals could do this and still hover in the air with enough precision to feed from flowers, swaying in the wind.
"We expected to see a tradeoff with the moths doing significantly worse at tracking flowers in low light conditions. What we saw was that while the moths did slow down, that only made a difference if the flower was moving rapidly — faster than they actually move in nature," Sponberg said.
Investigation of how hawkmoths are able to slow down their nervous systems in order to see at night was published in the journal Science.
