First published online March 14, 2008
Journal of Experimental Biology 211, 1021-1028 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.014555
Jumping in a wingless stick insect, Timema chumash (Phasmatodea, Timematodea, Timematidae)
Malcolm Burrows
Department of Zoology, University of Cambridge, Cambridge CB2 3EJ,
UK
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Fig. 1. Photographs of a female Timema chumash taken from the side (A),
ventrally (B) and dorsally (C).
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Fig. 2. Structure of the legs. (A) Photograph of a left hind leg viewed medially to
show the relative proportions of the different segments. (B) Drawings of a
hind, middle and front leg to show their relative sizes. (C) Photograph of the
femoro-tibial joint of the right hind leg viewed laterally. The arrows
indicate the constrictions in the distal femur and proximal tibia.
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Fig. 3. Jump to the right captured with high speed imaging at 1000 frames
s–1. (A) Sequence of images from the jump at the times
indicated. Take-off is achieved 13 ms after the first detectable movement of
the hind legs. (B) Top graph shows angular changes of the right hind leg and
the body during this jump. The four angles plotted and shown in the inset
diagram are: femoro-tibial joint of the right hind leg (filled circles); the
angle between the femur and the thorax (open circles), indicating the movement
of the whole hind leg because the coxa and trochanter could not be resolved in
these high speed images; the angle between the head and thorax (crosses); and
the angle of the thorax relative to the ground (open squares). Bottom graph
shows movements of the tip of the abdomen (triangles) and a point on the
thorax during the same jump (filled squares).
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Fig. 4. Images from two jumps by two Timema at the times indicated and
captured at 1000 frames s–1. (A) A jump from the front wall
viewed ventrally. The first movement of the hind legs occurred at –13 ms
before take-off. (B) A jump to the right and away from the camera viewed from
behind. The first movements of the hind legs occurred at –12 ms before
take-off.
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Fig. 5. Velocity and trajectory of five jumps by two Timema. (A) Peak
velocity plotted as three point rolling average against time. The maximum
velocity of the body is reached at –2 ms before take-off. (B)
Trajectories of the jump normalised for the same starting point and direction.
The open square on the cartoon shows the point on the thorax that was measured
for these graphs.
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Fig. 6. Complete trajectory of a forward jump. The position of three points on the
body are plotted [front of the head (diamonds), tip of the abdomen (triangles)
and the same position on the thorax as in
Fig. 5 (squares)]. Selected
frames from the sequence are shown at the times indicated. The cartoon in this
and subsequent figures shows Timema at the start of the jump to
emphasise the position of the hind legs.
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Fig. 8. Complete trajectory of a backwards somersault. The head initially points to
the left. The thrust of the hind legs pushes the tip of the abdomen downwards
to contact the ground and then forces the body backwards about this pivot
point. The insect finishes with its dorsal surface on the ground and its head
pointing toward the right.
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© The Company of Biologists Ltd 2008
