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Edited by A. J. Hudspeth, Howard Hughes Medical Institute, New York, NY, and approved March 28, 2012 (received for review January 6, 2012)
Abstract
Despite their small size, some insects, such as crickets, can produce high amplitude mating songs by rubbing their wings together. By exploiting structural resonance for sound radiation, crickets broadcast species-specific songs at a sharply tuned frequency. Such songs enhance the range of signal transmission, contain information about the signaler’s quality, and allow mate choice. The production of pure tones requires elaborate structural mechanisms that control and sustain resonance at the species-specific frequency. Tree crickets differ sharply from this scheme. Although they use a resonant system to produce sound, tree crickets can produce high amplitude songs at different frequencies, varying by as much as an octave. Based on an investigation of the driving mechanism and the resonant system, using laser Doppler vibrometry and finite element modeling, we show that it is the distinctive geometry of the crickets’ forewings (the resonant system) that is responsible for their capacity to vary frequency. The long, enlarged wings enable the production of high amplitude songs; however, as a mechanical consequence of the high aspect ratio, the resonant structures have multiple resonant modes that are similar in frequency. The drive produced by the singing apparatus cannot, therefore, be locked to a single frequency, and different resonant modes can easily be engaged, allowing individual males to vary the carrier frequency of their songs. Such flexibility in sound production, decoupling body size and song frequency, has important implications for conventional views of mate choice, and offers inspiration for the design of miniature, multifrequency, resonant acoustic radiators.
Footnotes
- ↵1To whom correspondence should be addressed. E-mail: natasha.mhatre{at}bris.ac.uk.
Author contributions: N.M., F.M.-Z., R.B., and D.R. designed research; N.M. and F.M.-Z. performed research; N.M. and F.M.-Z. analyzed data; and N.M. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
See Author Summary on page 8370 (volume 109, number 22).
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1200192109/-/DCSupplemental.
Changing resonator geometry to boost sound power decouples size and song frequency in a small insect
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