01984nas a2200181 4500008004100000022001400041245008600055210006900141260001600210300001600226490000800242520141700250100001801667700002101685700001901706700002601725856005101751 2018 eng d a0001-496600aThe micromechanics and bioacoustic behaviour of Bunaea alcinoe moth scales0 amicromechanics and bioacoustic behaviour of iBunaea alcinoeI mot cJan-09-2018 a1775 - 17750 v1443 a

Through the 65 million year acoustic arms race between moths and bats, different moth species have evolved different defence strategies against bat echolocation. For non-toxic moth species without hearing capability, passive acoustic camouflage is thought to be the most efficient way to evade bat predation. Being the elementary building blocks covering moth wing surfaces, scales have been hypothesized as the main organ creating such acoustic camouflage. There is, however, no understanding for the relation between scale microstructure and wing acoustic performance. This report represents the first effort to numerically and experimentally characterize moth scale biomechanics and vibrational behaviour. 3D microstructures of Bunaea alcinoe moth scales have been characterized using various microscopies. A parameterized finite element model has been built to replicate the double-layered perforated scale bio-nanomaterial. Both experimental and numerical analyses have proved that the first three resonance frequencies of a single scale lie within the bat echolocation frequency range. Here, we propose numerical models that explain how the resonances can contribute to the acoustic performance of wings. This study contributes to the on-going discussion of the evolution of ultrasonic camouflage in moths. We aim to use our findings to generate biomimetic light-weight noise mitigation materials.

1 aShen, Zhiyuan1 aNeil, Thomas, R.1 aRobert, Daniel1 aDrinkwater, Bruce, W. uhttp://asa.scitation.org/doi/10.1121/1.506785201618nas a2200181 4500008004100000022001400041245005500055210005500110260001600165300001600181490000800197520109600205100002101301700001801322700002601340700001901366856005101385 2018 eng d a0001-496600aStealthy moths avoid bats with acoustic camouflage0 aStealthy moths avoid bats with acoustic camouflage cJan-09-2018 a1742 - 17420 v1443 a

Intense predation pressure from echolocating bats has led to the evolution of a host of anti-bat defences in nocturnal moths. Some have evolved ears to detect the ultrasonic biosonar of bats, yet there are many moths that are completely deaf. To enhance their survival chances, deaf moths must instead rely on passive defences. Here, we show that furry morphological specializations give moth bodies and wing joints acoustic stealth by reducing their echoes from bat calls. Using acoustic tomography, echo strength was quantified in the spatial and frequency domains of two deaf moth species that are subject to bat predation and two butterfly species that are not. Thoracic fur determines acoustic camouflage of moths but not butterflies. Thoracic fur provides substantial acoustic stealth at all ecologically relevant ultrasonic frequencies, with fur removal increasing a moth’s detection risk by as much as 38%. The thorax fur of moths acts as a lightweight porous sound absorber, facilitating acoustic camouflage and offering a significant survival advantage against bats.

1 aNeil, Thomas, R.1 aShen, Zhiyuan1 aDrinkwater, Bruce, W.1 aRobert, Daniel uhttp://asa.scitation.org/doi/10.1121/1.5067725