First published online February 15, 2008
Journal of Experimental Biology 211, 678-685 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.013920
Thoracic vibrations in stingless bees (Melipona seminigra): resonances of the thorax influence vibrations associated with flight but not those associated with sound production
Michael Hrncir1,2,*,
Anne-Isabelle Gravel3,
Dirk Louis P. Schorkopf2,
Veronika M. Schmidt2,
Ronaldo Zucchi1 and
Friedrich G. Barth2
1 Department of Biology, University of São Paulo, FFCLRP, Av.
Bandeirantes 3900, 14040–901 Ribeirão Preto, SP, Brazil
2 Department of Neurobiology and Cognition Research, University of Vienna,
Althanstrasse 14, A-1090 Vienna, Austria
3 Department of Biology, York University, 4700 Keele Street, Toronto, Ontario,
M3J 1P3, Canada
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Fig. 1. Stingless bees of the genus Melipona generate pulsed annoyance
buzzing when tethered by a sling around their neck. (A) Sling-tethering
method, showing the sling (S) formed by a nylon thread (T) guided through an
injection needle (IN). Sy, syringe for fixing the thread. Vibrations were
measured on the thorax (Tx), the distal mesothoracic femur (Fe), and the
wingtips (Wt) using a laser vibrometer. Photo showing a sling-tethered worker
of M. rufirentris. (B) The following parameters of the pulsed
vibrations were analysed: velocity amplitude (VA), duration of single
pulses (PD), and pulse sequence (PS). In addition the
frequency spectra (C) provided the main frequency component (MF). (D)
The displacement component (red line; DA: displacement amplitude) of
the vibrations was derived by integrating the vibration velocity recorded by
the laser vibrometer (black line).
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Fig. 2. Build-up and decay phase of vibratory pulses. The first 15 and the last 15
cycles of a vibratory pulse (A) were analysed regarding cycle amplitude (B)
and cycle frequency (C). Line-plots, left y-axis: absolute values for
velocity (V) and cycle frequency (Cycle freq.). Open circles, right
y-axis: relative values (percentage of maximum of velocity
Vp-p, and main frequency MF, respectively).
Arrows indicate the cycle numbers where the 95% threshold of build-up and
decay is attained. Size of gap: 0–600 cycles.
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Fig. 3. Examples for thoracic vibrations during flight (A,B), annoyance buzzing
(C,D) and forager vibrations (E,F). (A–F) Two cycles of the different
types of thoracic vibrations showing the velocity (V, black lines)
and the displacement (D, red lines). Arrows indicate high frequency
components superimposed on the fundamental oscillation.
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Fig. 4. Build-up and decay (shaded area) of cycle velocity (A–C) and cycle
frequency (D–F) of thoracic oscillations during stationary flight (A,D;
filled squares, N=15), during annoyance buzzing (B,E; filled circles,
N=15), and during forager vibrations (C,F; open circles,
N=15). Graphs show the means ± s.d. of relative values
(percent of the maximum velocity or of the main frequency, MF).
Broken lines indicate 95% of maximum.
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Fig. 5. Effect of wing removal on the thoracic vibrations during flight
(A–C), and during annoyance buzzing (D–F) of 12 sling-tethered
bees. (A,D) Main frequency; (B,E) velocity amplitude; (C,F) displacement
amplitude; WW, intact bees; WO, OO, bees after removal of one or both
wing-pairs. Asterisks indicate significant differences between the indicated
treatments (Dunn's test for pairwise comparison: P<0.05). See text
for statistics. Box plots indicate inter-quartile range (box), the median
value (horizontal line), 95% range (whiskers) and outliers of all data.
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Fig. 6. Effect of increasing the mass of the oscillating system on the thoracic
vibrations during flight (A–C), and during annoyance buzzing (D–F)
of 15 sling-tethered bees. (A,D) Main frequency; (B,E) velocity amplitude;
(C,F) displacement amplitude; –ma, bees before adding mass; +ma, bees
after gluing a tiny piece of lead onto the thorax. The additional mass almost
doubled that of the thorax. Asterisks indicate significant differences between
the treatments (paired t-test: P<0.05). See text for
statistics. Box plots indicate inter-quartile range (box), the median value
(horizontal line), 95% range (whiskers) and outliers of all data.
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Fig. 7. Oscillations of legs and wings going along with thorax vibrations.
Comparison of various parameters of vibrations registered simultaneously on
the thorax Tx, and on the mesothoracic femur Fe (A), or on the wingtips Wt
(B). Filled symbols: annoyance buzzing, AB (A: N=7, n=140;
B: N=16, n=320); open symbols: forager vibrations, FO (A:
N=9, n=200; B: N=16, n=320).
rS, correlation coefficient. See text for statistics.
V, velocity; MF, main frequency; PD, pulse
duration; PS, pulse sequence.
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© The Company of Biologists Ltd 2008
