First published online June 16, 2004
Journal of Experimental Biology 207, 2691-2703 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.01096
Wing hair sensilla underlying aimed hindleg scratching of the locust
Keri L. Page* and
Thomas Matheson
Department of Zoology, University of Cambridge, Downing Street,
Cambridge CB2 3EJ, UK
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Fig. 6. Distribution of hairs within 9 stimulus regions. Medium length hairs
occurred primarily on the subcosta (see
Fig. 4), which runs through
leading edge regions 6–9. Long hairs occurred primarily on the
postcubitus (see Fig. 4), which
runs through trailing edge regions 1–4. (C) Schematic representation of
stimulus regions 1–9 and their relationship with the principal wing
veins. (A) Long hairs on the postcubitus were distributed evenly across the
trailing edge regions. Note that the region 4 included the cluster of long
hairs at the distal end of the postcubitus. (B) The density of medium hairs on
the subcosta was greatest in region 8. Females had more medium and long hairs
than males in all regions (A,B). Boxes indicate the interquartile range,
containing 50% of values, whiskers indicate the range, and horizontal lines
within boxes indicate the median. Where there was no variability, only the
median is shown as a horizontal line.
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Fig. 1. Trichoid hair types present on the dorsal surfaces of the forewings of
Schistocerca gregaria. (A) Distribution of hair lengths measured from
SEMs. Grey boxes highlight the trimodal nature of the distribution. (B) Short
hair with socket (arrowhead). (C) Enlargement of the pore at the tip of the
shaft of the short hair shown in B (arrowhead). (D) Medium length hair with
socket but no pore. (E) Medium length hairs on the subcosta vein point towards
the leading and trailing edges at irregular intervals. The trailing edge is
up, distal is to the right. (F) Long hair on the postcubitus vein, with socket
but no pore. (G) A variety of hair-like structures on a wing vein (black
arrowhead) and on the wing membrane (white arrowhead) of the hindwing anal
region. (H) The shorter hair-like structures on the hindwings are variable in
length and do not insert into a socket. (I) Longer hair-like structures on the
proximal 10–15 mm of a forewing, near the wing's articulation with the
thorax. (J) Enlargement of the long hair-like structures near a forewing's
articulation. These longer structures do not have a socket (arrowheads) or a
pore at the tip.
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Fig. 2. Characterisation of trichoid hairs on the wings. (A) Two sections of a
continuous recording from a basiconic sensillum on the dorsal surface of a
forewing. One afferent responded with an 800 ms burst of spikes after the
electrode was first placed over the intact tip of the sensillum (upper trace).
After the afferent fell silent, a brief movement of the sensillum (horizontal
bar) elicited a burst of spikes in a second afferent that had larger amplitude
spikes (lower trace). (B) The afferent of a long hair on the postcubitus vein
of the upper surface of a forewing responded with a burst of spikes to a brief
movement of the hair (bar). The recording was made from the cut shaft. (C,D,F)
Recordings from the cut shafts of medium length hairs on the ventral surface
of a forewing (C), dorsal surface of a hindwing (D) and ventral surface of a
hindwing (F). In all cases, movement (bars) elicited a burst of spikes in a
single afferent. (E) Two sections of a continuous recording from a basiconic
sensillum on the ventral surface of a hindwing. One afferent responded with a
600 ms burst of spikes after the electrode was first placed over the intact
tip of the sensillum (upper trace). After the afferent fell silent, a brief
movement of the sensillum (horizontal bar) elicited a burst of spikes in a
second afferent that had a different waveform (lower trace). Basiconic
sensilla were not seen on the ventral surface of the forewings or dorsal
surface of the hindwings.
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Fig. 3. Schematic representation of the average distribution of trichoid hairs on
the dorsal surface of a locust forewing (based on N=5 detailed
drawings). (A) The principal veins of the forewing, named according to
Albrecht (1953 ). The vannus
region of the trailing edge is delineated by the claval furrow (broken line)
that lies between the postcubitus and vannal veins. The furrow forms a hinge
so that at rest the vannus is folded over the dorsal surface of the animal,
i.e. the vannus of one wing overlaps the vannus of the other (see
Fig. 5A). (B,C) Average
distribution of the three types of hairs on the forewings of female (B) and
male (C) locusts. The total numbers were counted per vein in five animals and
the mean numbers are indicated here (each colour-coded dot represents one
hair). This representation does not reflect the exact locations of hairs in
any one preparation. Basiconic sensilla occurred on many of the veins (red
dots) whereas medium length hairs occurred in greatest numbers on the subcosta
(light blue dots) and long hairs occurred only on the postcubitus (dark blue
dots). Black arrowheads indicate long hairs that were counted as part of the
wingtip region.
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Fig. 4. The density of each of the three hair types on the principal veins of the
dorsal surface of the forewings in male and female locusts. (A) Basiconic
sensilla occurred on all of the veins but were most numerous on the subcosta.
(B) Medium length hairs occurred primarily on the subcosta. (C) Long hairs
were restricted to the postcubitus and wing tip. Values are means ±
S.D., N=5 animals. There were no differences in
the densities of basiconic sensilla on male and female forewings (A), but
females had significantly more medium hairs on the subcosta than did males
(B), and more long hairs on the postcubitus than did males (C). Filled
squares, males; open squares, females.
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Fig. 5. (A) When the wings are folded, the vannus of one wing (here the right)
folds over the other, bending at the claval furrow (yellow arrows). The
asterisk indicates the trailing edge of the right wing. Long hairs on the
postcubitus (e.g. arrowheads) stand up vertically above the animal's dorsal
surface in two rows. (B) The long hairs point dorsally and slightly
posteriorly. (C) The row of long hairs on the postcubitus of the left wing
glint in the light, indicating clearly their length relative to the depth of
the wing. Those on the right wing cannot be seen here because they are in
shadow. Scale bar, 1 mm (A); 2 mm (B); 5 mm (C).
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Fig. 7. The probability of eliciting an ipsilateral scratch differed when different
regions on the dorsal surface of a forewing were stimulated. The probability
of eliciting a scratch was generally higher for trailing edge regions
1–4 (A) than for leading edge regions 6–9 (B). Females had a
higher likelihood of scratching than males for all regions except the wing tip
(region 5; A, C). All of the scratches analysed started with the tarsus in the
anterior start position (C). Wing regions are indicated with coloured
numerals, and the claval furrow is indicated by a broken line. The vannal
region of the wing above the claval furrow is normally folded across the
dorsal surface of the body, but is shown here flattened out. Dotted arrows
indicate corresponding wing regions in both histograms. Boxes indicate the
interquartile range, containing 50% of values, whiskers indicate the range,
and horizontal lines within boxes indicate the median. Where there was no
variability, only the median is shown as a horizontal line.
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Fig. 8. Ablating long hairs on the postcubitus (in trailing edge regions 1–4)
had a significant effect on the likelihood of eliciting a scratch when
stimulating any of the regions 1–9. (A) Following ablation the
probability of eliciting a scratch declined for the trailing edge regions
1–4, but increased for the wingtip region 5. (B) Following ablation the
probability of eliciting a scratch increased for leading edge regions
6–9. (C). Wing regions are indicated with coloured numerals, and the
claval furrow is indicated by a dashed line. The vannal region of the wing
above the claval furrow is normally folded across the dorsal surface of the
body, but is shown here flattened out. Dotted arrows indicate corresponding
wing regions in both histograms. Boxes indicate the interquartile range,
containing 50% of values, whiskers indicate the range, and horizontal lines
within boxes indicate the median. Where there was no variability, only the
median is shown as a horizontal line.
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© The Company of Biologists Ltd 2004
