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First published online December 16, 2008
Journal of Experimental Biology 212, 106-115 (2009)
Published by The Company of Biologists 2009
doi: 10.1242/jeb.024448
Jumping strategies and performance in shore bugs (Hemiptera, Heteroptera, Saldidae)
Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
Author for correspondence (e-mail: mb135{at}hermes.cam.ac.uk)
Accepted 10 November 2008
The jumping movements of the hemipteran shore bug (Saldula
saltatoria, sub-order Heteroptera, family Saldidae) were analysed from
sequences of images captured at 5000 frames s–1. Adult
Saldula weigh
2.1 mg and are
3.5 mm long. The hind legs
that propel jumping are 180% longer than the front legs and 90% of body
length, but non-jumping species in the same family have longer hind legs
relative to the lengths of their bodies. Jumps were powered by large
trochanteral depressor muscles in the thorax in two different strategies. In
the first (used in 24% of jumps analysed), a jump was propelled by
simultaneous extension of the two hind legs powered by rapid depression
movements about the coxo-trochanteral joints, while both pairs of wings
remained closed. In the second strategy (74% of jumps), the wings were opened
before the hind legs began to move. At take-off, the position of the wings was
variable and could be 8–21 ms into either elevation or depression. When
the hind legs alone propelled a jump, the body was accelerated in
3.97±0.111 ms at a take-off angle of 52±6.5° to a take-off
velocity of 1.27±0.119 m s–1; when the wings also
moved, the body was accelerated in 3.86±0.055 ms at a take-off angle of
58±1.7° to a take-off velocity of 1.29±0.032 m
s–1. These values are not different in the two jumping
strategies. In its best jumps the take-off velocity reached 1.8 m
s–1 so that Saldula experienced an average
acceleration of 529 m s–2, equivalent to almost 54g, expended
3.4 µJ of energy, while exerting a force of 1.1 m N. The power requirements
for jumping indicate that a catapult mechanism must be used in which the
trochanteral depressor muscles contract and store energy in advance of a jump.
These jumps should propel it to a height of 105 mm or 30 times its body length
and distances of 320 mm. The two jumping strategies achieve the same jumping
performance.
Key words: kinematics, Heteroptera, locomotion
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