Hawkmoths Slow their Brains for Better Night Vision

Hawkmoths have the tough task of hovering mid-air to obtain their favorite flower nectar, even in the dark, but new fascinating research shows that these insects can slow down their brains for better night vision - while continuing to perform demanding tasks.

"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," researcher Simon Sponberg, an assistant professor in the School of Physics and School of Applied Physiology at the Georgia Institute of Technology, said in a statement.

The hummingbird-sized hawkmoth (Manduca sexta) is a nocturnal or crepuscular flying moth, meaning it only flies at dusk or dawn. Scientists already knew that the hawkmoth uses specialized eye structures to maximize the amount of light they can capture. But they also suspected that the insects might be slowing their nervous systems to make the best use of this limited light.

However, by slowing down their brains, wouldn't that hurt their ability to hover and track the motion of flowers?

To find out, Sponberg and colleagues at the University of Washington conducted experiments using high-speed infrared cameras and 3-D-printed robotic flowers. The flowers, which contained the hawkmoth's favorite nectar, could be moved from side-to-side at different rates.

While varying both the light conditions and the frequency at which the flowers moved (up to 20 hertz), the researchers studied how well free-flying moths kept their tongues - known as proboscises - in the flowers.

They also measured real flowers blowing in the wind to determine the range of motion the insects had to overcome in the wild.

"We expected to see a trade-off with the moths doing significantly worse at tracking flowers in low light conditions," said Sponberg. "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."

Since the moth's wings beat at a rate of about 25 strokes per second, they had to adjust their direction of movement with nearly every wingstroke.

"This is really an extreme behavior, though the moth makes it look simple and elegant," Sponberg explained. "To maneuver like this is really quite challenging. It's an extreme behavior from both a sensory and motor control perspective."

While this revelation is fascinating to scientists, it also holds promise for some real world applications. It could help the next generation of small flying robots operate efficiently under a broad range of lighting conditions, researchers say.

The findings were published in the journal Science.

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