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First published online December 1, 2006
Journal of Experimental Biology 209, 4923-4937 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02608

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Generation of extreme ultrasonics in rainforest katydids

Fernando Montealegre-Z^1,*, Glenn K. Morris² and Andrew C. Mason¹

¹ Integrative Behaviour and Neuroscience Group, Department of Life Sciences, University of Toronto at Scarborough, 1265 Military Trail, Scarborough, Ontario, Canada, M1C 1A4
² Department of Biology, University of Toronto at Mississauga, 3359 Mississauga Road, Mississauga, Ontario, Canada, L5L 1C6

^* Author for correspondence: (e-mail: f.montealegre{at}utoronto.ca)

Accepted 19 October 2006

The calling song of an undescribed Meconematinae katydid (Tettigoniidae) from South America consists of trains of short, separated pure-tone sound pulses at 129 kHz (the highest calling note produced by an Arthropod). Paradoxically, these extremely high-frequency sound waves are produced by a low-velocity movement of the stridulatory forewings. Sound production during a wing stroke is pulsed, but the wings do not pause in their closing, requiring that the scraper, in its travel along the file, must do so to create the pulses. We hypothesize that during scraper pauses, the cuticle behind the scraper is bent by the ongoing relative displacement of the wings, storing deformation energy. When the scraper slips free it unbends while being carried along the file and its deformation energy contributes to a more powerful, higher-rate, one-tooth one-wave sound pulse, lasting no more than a few waves at 129 000 Hz. Some other katydid species make pure-tone ultrasonic pulses. Wing velocities and carriers among these pure-tone species fall into two groups: (1) species with ultrasonic carriers below 40 kHz that have higher calling frequencies correlated with higher wing-closing velocities and higher tooth densities: for these katydids the relationship between average tooth strike rate and song frequency approaches 1:1, as in cricket escapement mechanisms; (2) a group of species with ultrasonic carriers above 40 kHz (that includes the Meconematinae): for these katydids closing wing velocities are dramatically lower and they make short trains of pulses, with intervening periods of silence greater than the duration of the pulses they separate. This signal form may be the signature of scraper-stored elastic energy.

Key words: Orthoptera, Tettigoniidae, ultrasound, bioacoustics, elastic, stridulation, resilin, katydid

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