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Moth Develops Ultrasonic Weapon To Fend Off Bats, Scientists Find

Ermine moths use unique acoustic defense mechanism to produce ultrasounds equivalent to human conversation

A moth has developed an ultrasonic weapon to warn off predatory bats.

Scientists have discovered that the species has evolved a very special acoustic defense mechanism against their echolocating carnivores.

The research team found that ermine moths produce ultrasonic clicking sounds twice per wingbeat cycle.

Yet, the moths are entirely unaware of their unique defense mechanism as they lack hearing organs.

University of Bristol researchers set out to discover how exactly the weapon works.

The research team found that ermine moths produce ultrasonic clicking sounds twice per wingbeat cycle. PHOTO BY HERNALDO MENDOZA/SWNS 

The findings, published in the journal Proceedings of the National Academy of Sciences (PNAS), show that a part of the moths’ hindwings snap through as the wings fold during flight.

The sudden snap vibrates through an adjacent membrane, amplifying the strength and direction of this sound. The sound-producing organ is called an aeroelastic tymbal.

First author Dr. Hernaldo Mendoza Nava said: “Sound production and radiation is linked to mechanical vibration, for example in the skin of a drum or a loudspeaker.

The research team found that ermine moths produce ultrasonic clicking sounds twice per wingbeat cycle. PHOTO BY HERNALDO MENDOZA/SWNS 

“In ermine moths, the snap-through buckling events act like drumbeats at the edge of a tymbal drum, exciting a much larger portion of the wing to vibrate and radiate sound.

“As a result, these millimeter-sized tymbals can produce ultrasounds at the equivalent level of a lively human conversation.”

To uncover more about how this works, the team created a computer simulation of the snap-through response and sound production that matches recorded moth signals in frequency, structure, amplitude, and direction.

Professor Marc Holderied said: “Our goal in this research was to understand how the corrugations in these tymbals can buckle and snap through in a choreographed way to produce a chain of broadband clicks.

“With this study, we unfolded the biomechanics that triggers the buckling sequence and shed light on how the clicking sounds are emitted through tymbal resonance.”

Dr. Rainer Groh added: “The integration of various methods across the sciences with a consistent information flow across discipline boundaries in the spirit of ‘team science’ is what made this study unique and a success.

“In addition, without the amazing modern capabilities in imaging, data analysis and computation, uncovering the mechanics of this complex biological phenomenon would not have been possible.”

The researchers hope that their findings will help build on the understanding of many other similar insects.

Professor Alberto Pirrera added: “In the realm of engineering design, nonlinear elastic responses, such as buckling and snap-through instabilities, have traditionally been perceived as failure modes to be avoided.

“In our research, we have been advocating a paradigm shift and have demonstrated that buckling events can be strategically leveraged to imbue structures with smart functionality or enhanced mass-efficiency.

“The natural world, once again, serves as a source of inspiration.”

Produced in association with SWNS Talker

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