Under the darkness of night, bats use soundwaves to find moths to eat. However, these insects are not completely defenseless against bats. Some moths use their wings to produce an ultrasonic warning sound against winged mammals. The findings are described in a study published February 5 in the journal Proceedings of the National Academy of Sciences (PNAS).
[Related: Why artificial light—and evolution—trap moths.]
A genus of moths called Yponomeuta (or ermine moths) click twice per wingbeat cycle using a small ridged membrane located in their hindwing. These moths do not have hearing organs and thus do not appear to be aware that they are even making these sounds and they can’t even control the sound using muscular action.
Defenses like these can help the moths thwart the bats by annoying them and save them from becoming a meal, even if only temporarily. Decoding the mechanics of how this works in moths could help researchers better understand more intricate aspects of the way insects produce sounds for self-defense.
In the study, a team of engineers and biologists from the University of Bristol in England looked at how the individual ridges that make up a corrugated patch in the ermine moth’s hindwings snap. This sudden snap-through buckling vibrates the membrane that is next to the hindwing. The strength and direction of the sound is then amplified like how the skin of a drum or a speaker makes a sound louder. This sound-producing organ in moths is called an aeroelastic tymbal.
“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,” study co-author and mechanical engineer Hernaldo Mendoza Nava said in a statement. “As a result, these…
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