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First published online March 21, 2005
Journal of Experimental Biology 208, 1219-1237 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01526
The mechanics of sound production in Panacanthus pallicornis (Orthoptera: Tettigoniidae: Conocephalinae): the stridulatory motor patterns
1 Department of Zoology, University of Toronto at Mississauga, 3359
Mississauga Road, Mississauga, Ontario, Canada, L5L 1C6
2 Integrative Behaviour and Neuroscience Group, Department of Life Sciences,
University of Toronto at Scarborough, 1265 Military Trail, Scarborough,
Ontario, Canada, M1C 1A4
* Author for correspondence (e-mail: fmonteal{at}utm.utoronto.ca)
Accepted 27 January 2005
To examine whether sound production in katydids relies on an escapement
mechanism similar to that of crickets we investigated the functional anatomy
and mechanical properties of the stridulatory apparatus in the katydid
Panacanthus pallicornis. Males of this species produce sustained
pulses with a sharp low frequency peak of 
5 kHz and a broad band spectrum
between 15 and 25 kHz. Simultaneous recordings of movement and sound indicate
that the entire stridulatory file is used for sound production and there is
nearly a 1:1 correspondence between the number of cycles in a song and the
number of teeth on the file. There is an overall tendency for both the spacing
of teeth to increase along the file and the velocity of wing closure to
increase as the scraper traverses the file. There is considerable variation,
however, in the evenness of tooth spacing and in the instantaneous velocity of
wing closure during sound production. The production of sustained pulses
appears to depend on resonance in the right tegmen, with the left tegmen
acting primarily as a damping element. This resonance is not strongly coupled
to the scraper and, unlike crickets, the timing of file-scraper interactions,
and therefore the phasing of energy input to wing oscillations, is variable.
Similarly, the quality of the sound spectrum varies over the course of a
single stridulatory wing-stroke. Based on measurements of tooth spacing on the
stridulatory file and cycle-by-cycle frequency of sound output, we predicted
the velocity of wing movement that would provide consistent phasing of
file-scraper interactions with respect to sound-radiating wing oscillations
and compared this with measurements of wing velocity. Acceleration of wing
velocity during stridulation results in a closer match to the velocity
required for optimal phasing during a portion of the call, and this
corresponds with higher amplitudes of radiated sound and the excitation of
higher order modes of vibration (evident as distinct harmonic peaks in
spectrograms). Our results suggest that in katydid stridulation, the movement
of the scraper along the file is not regulated by an escapement mechanism as
it is in crickets. Instead, katydids that produce pure-tone songs sweep their
wings over a range of velocities, within which some portion matches file tooth
spacing to give optimal phasing of energy input to excite a resonance in the
right tegmen.
Key words: sound production, katydid, Panacanthus pallicorni, resonance, stridulatory mechanisms, biomechanics, bush cricket, wing movements, stridulation
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