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In This Issue

Some species of moths escape echolocation by bats by using acute hearing that triggers evasive flights or by producing ultrasound clicks that telegraph the presence of defensive toxins, startle bats, or scramble bats’ biosonar. Zhiyuan Shen et al. (pp. 12200–12205) attempted to determine how nontoxic moth species without such fine hearing keep bats at bay. Using confocal and scanning electron microscopy, the authors analyzed the 3D nanostructure of the elaborately sculpted scales covering the forewings of the cabbage tree emperor moth (Bunaea alcinoe). Analysis of the vibration dynamics of an individual moth scale revealed that the scales vibrate at resonant frequencies—28.4, 65.2, and 153.1 kHz—that overlap with bats’ biosonar range, 20–150 kHz, creating acoustic camouflage. In contrast, resonant properties of butterfly-like scales fell outside the range relevant to bat echolocation. The moths’ perforated scales, arrayed across the forewing surfaces, likely transmit or absorb bats’ probing ultrasonic waves, minimizing backscatter and evading detection. Thus, the authors suggest, the moths’ scales act as resonant absorbers that represent an evolutionary adaptation against biosonar. According to the authors, the findings could aid the design of biologically inspired sound absorbers for an array of applications, including noise mitigation, building acoustics, and target concealment for military use. — P.N.