Jumping in a winged stick insect
Malcolm Burrows* and
Oliver Morris
Department of Zoology, Downing Street, University of Cambridge,
Cambridge CB2 3EJ, UK
Present address: Department of Physiology, Royal Free and University College
Medical School, London NW3 2PF, UK
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Fig. 1. Morphometry and mass of the body. (A) Photographs of an adult male
Sipyloidea to show the elongated body and long thin legs. Scale bar,
5 mm. The inset shows a close-up of the femorotibial joint of a hind leg,
which lacks any clear specialisations for jumping. Scale bar, 0.5 mm. (B,C)
Bar charts showing the dimorphic body mass (B) and body length (C) of adult
males (M) and females (F). Values are means ± S.E.M. Values of
N are given on the graphs. (D,E) Pie charts of the distribution of
mass in different parts of the body (as a percentage of total body mass) in
three males (D) and six females (E).
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Fig. 2. Resting posture and responses to tactile stimulation of the abdomen. (A)
Histograms of the different postures adopted by nymphs, by adult males and by
adult females. (B) The responses of the same three groups of insects to an
initial touch to the abdomen. (C) The responses to the same stimulus delivered
5 s after the preceding response had stopped. (D) Choice trees of the
responses to touch; data as in B and C. The five choices made by adults are
shown but, because nymphs cannot fly, they can make only four choices. The
thickness of a line represents the frequency with which that choice was made.
Forty adult males, 28 adult females and 56 nymphs were used.
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Fig. 3. A jump by a nymph from a horizontal stance. (A) Selected images from a jump
captured at 250 Hz. The timing of the images refers to the graphs in B and the
outlines in C. Take-off occurred at 0 ms. (B) Graph of the changes in angle of
the joints between the meso- and metathorax (m/m in the inset diagram of the
insect), between the metathorax and abdomen (m/a) and between the femur and
tibia (f/t) of a hind leg. The change in height of the mesothoracic coxa above
the ground is also plotted (Body height). Each point is measured from
contiguous images separated in time by 4 ms. The vertical yellow bars indicate
when the legs lost contact with the ground and when take-off occurred at 0 ms.
The same colour coding is used in subsequent figures. (C) Tracings of the
movements of the head, thorax and abdomen during the jump. The jump trajectory
was forwards and downwards with a take-off velocity of 0.8 m
s-1.
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Fig. 5. An adult male jumping and launching into flapping flight. (A) Selected
images from the jump sequence. The abdomen is curled forwards as the wings are
elevated and then moves backwards as the wings are depressed. (B) Graphs of
the changes in the angles of the joints between the meso- and metathorax
(m/m), between the metathorax and abdomen (m/a) and between the femur and
tibia (f/t) of a hind leg. The height of the tip of a hind wing and the height
of the body above the ground are also plotted. The take-off velocity was
0.6ms-1 at an angle of 10°, so that the trajectory was forwards
and upwards.
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Fig. 4. Movements of the body during jumping. (A) A single frame at time -60ms is
shown from the jump by a nymph starting at -108ms and ending at +60ms with
take-off at 0ms (highlighted in black boxes) and with each frame separated by
4ms. The positions of four fixed points on the body are superimposed onto this
frame: the tip of the abdomen (yellow), the joint between the metathorax and
abdomen (dark blue), the joint between the meso- and metathorax (pink) and the
position of the head (light blue). As the abdomen is thrust upwards and
forwards, the insect rocks backwards. When the abdomen reaches the peak of its
forward movement and reverses to move backwards, the body is accelerated
forwards. The take-off trajectory is forwards and downwards. (B) Changes in
the centre of mass of a male during a jump plotted in relation to the
movements of the tip of the abdomen and the joint between the meso- and
metathorax. The sequence lasts from -140 to +28ms, with take-off at 0ms. At
-44ms, the middle legs are fully extended; at -16ms, both hind legs are fully
extended. The scale is the same as in A.
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Fig. 6. A male taking off and flying without jumping. (A) Selected images of the
take-off starting from an initial position in which the long axis of the body
is inclined upwards by 25°. (B) Graphs of the changes in the angles of the
joints between the meso- and metathorax (m/m), between the metathorax and
abdomen (m/a) and between the femur and tibia (f/t) of a hind leg. The height
of the tip of a hind wing and the height of the body above the ground are also
plotted. (C) Tracings of the movements of the abdomen, thorax and head during
the jump. The abdomen is not flicked forwards during the movement. The
take-off velocity was 0.9 m s-1 and the angle of the thorax
relative to the ground was 30°, so that the trajectory was forwards and
upwards.
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Fig. 7. Rapid backward movement of a nymph following a tactile stimulus to the
head. (A) Selected frames from the whole sequence. In the first frame, at 0
ms, the insect stands erect and then starts to collapse backwards so that at
120 ms the abdomen rests on the ground. (B) Graph of the changes in angle
between a hind femur and the body and between the femur and tibia of a hind
leg. The angles are marked in the first frame of A. The height of the body and
the horizontal, backward displacement of the head are also plotted.
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Fig. 8. Variations on backward movements by nymphs. (A) The insect stands erect and
then moves rapidly backwards without lowering its body height so that it
launches into a backward and downward jump from the platform. The position of
the head in each frame from this 80 ms sequence is plotted in frame 0 ms. (B)
The initial posture (0 ms) is a mimic of a twig in which all the legs are held
parallel to the long axis of the prostrate body. The body is then pulled
backwards away from a tactile stimulus to the head. The circles in the first
frame (0 ms) measured from each frame in the 120 ms sequence show the backward
movement of the head.
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Fig. 9. A backward jump by a nymph from an initial vertical posture. Selected
frames from the sequence in which take-off occurred at 0 ms are arranged in
two columns. The position of the head and the tip of the abdomen and the
distance of the body from the vertical pillar are plotted in the bottom two
frames. The abdomen is flicked forwards and the body moves upwards before the
legs lose contact with the pillar and the insect falls in a trajectory away
from the pillar.
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Fig. 10. Variations in backward jumping from a vertical posture by an adult male.
(A) Jumping is accompanied by flapping movements of the wings. Three frames
are shown from the selected sequence in which take-off occurred at 0 ms. The
wing movements propel the insect further from the pillar as it falls. (B) The
insect falls, but the abdomen is not flicked forwards. The movements of the
tip of the abdomen and the head are plotted in the bottom of three selected
frames from the whole sequence.
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© The Company of Biologists Ltd 2002
