All this time, moths have been using stealth invisibility cloaks, while Monarch butterflies continue to surprise with their ability to migrate 2,000 miles. As technologically advanced as we like to think we are, engineers have nothing on nature.
First, Professor Marc Holderied, a bio-acoustician from the University of Bristol who has studied bat echolocation for two decades, is developing “bio-inspired sound absorbers” inspired by moth wings. The result could include sound-absorbing “sonic wallpaper.” One potential application would be helping combat noise pollution in urban environments or anywhere.
Moths are Using Acoustic Invisibility Cloaks
While flowers have evolved to attract pollinating bats with an “acoustic equivalent of color,” moths are not trying to attract any bat. Rather, the “acoustic arms race” over 60 million years led to ingenious scales on the moth’s wings that help them hide like invisibility cloaks. Their furry bodies also help them to stay off the menu.
Moths may have no ability to detect bats through hearing, but they have the advantage of acoustic camouflage. When they fly, they make fewer echos that reveal them to a bat’s biosonar.
Holderied says the moth wings act as an acoustic metamaterial, a one-of-its-kind in nature. Each tiny scale vibrates at its unique frequency, collectively absorbing sound 10% more efficiently than any man-made sound absorber. Imagine rolling on some sonic wallpaper and getting a significantly better sound-insulated room! Apartment dwellers everywhere could take advantage of such material.
Video by Science X:
A Secret in a Monarch Butterfly’s Spots
Next, Andy Davis, a biologist at the University of Georgia, published a study about Monarch butterflies. The study indicates that the pattern of black and white spots on the butterfly wings may be much more than just pretty. While a male Monarch can be identified by two black spots on the hind wings, it’s the white spots at the border of the wing that could help them fly.
“This just might be the most exciting project I’ve ever worked on, because the findings not only uncover something previously unknown about monarchs, but they also have some real-world application for the aerospace industry!” wrote Davis.
Bioinspiration from Butterfly Wings
Davis and undergraduate Tina Vu teamed up with a mechanical engineer in the field of “bioinspiration,” Mostafa Hassanalian, from the New Mexico Institute of Mining and Technology.
Initially, the scientists thought butterflies with more black pigment would have a flight advantage, as with some bird wings. However, they discovered the opposite was true. Butterflies with more white pigment spots on the black edge of their wings may have an advantage in flying thousands of miles to Mexico in two months.
The pattern of dots possibly creates tiny eddies of rising air, assisting the butterflies’ journey by reducing aerodynamic drag.
“The researchers’ working theory is that the spots reduce drag by creating pockets of heating and cooling on the wing edge, which could create tiny eddies of rising air. The difference is subtle: The butterflies that completed the migration were only about 3 percent spottier than the ones at the starting line. But the scientists suspect that even a small reduction of drag could make a tangible difference in flight capabilities,” the New York Times reported.
Did the Monarch’s Migration Give Them Their Spots?
Butterflies photographed in Mexico may have more contrasting white on their wings. The pattern may be due to natural selection and not a color change. Incredibly, Davis notes that their migration may have given Monarch butterflies those spots. It makes you wonder if there could be numerous similar overlooked examples in nature everywhere.
“I suspect that this pattern has largely gone unnoticed for decades,” Davis wrote.
Davis previously found that the shade of orange on a Monarch correlates with flight ability.
Next, the researchers will experiment with artificial monarch wings in a wind tunnel to test the hypothesis. If proven, applying a layer of paint to a flight vehicle’s wings could be simple.
Mechanical engineer Hassanalian previously found that the colors of animal wings or flippers can affect flight performance. Recently, his flapping drones made of taxidermy birds became a viral sensation. (see video below).
Video by KRQE: