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Fig. 6. Significance of the spatial distribution of spiracle exchange areas for (A)
IFM mechanical power output, (B) flight muscle efficiency, (C) lift
coefficient, and (D) aerodynamic efficiency. Data show the relative difference
(
) in performance between unmanipulated flies and animals in which up
to 4 thoracic spiracles have been sealed during flight. The differences are
scaled to the performance of the unmanipulated control group. Performance
scores are plotted against total diffusive area of the animal's abdominal and
thoracic spiracles that may participate in tracheal gas exchange. Due to the
reduction of maximum flight force production with decreasing total spiracle
opening area, data are calculated at 0.29 (493 µm2 total
spiracle area), 0.48 (3780 µm2), 0.74 (5424 µm2),
1.01 (7889 µm2) and 1.36 (10 355 µm2) relative
flight force production for 04 thoracic spiracles open, respectively. A
value of 1.0 normalized force means that the fly produces a flight force equal
to body weight. Grey areas in the pictograms indicate maximum total spiracle
opening area available for respiratory gas exchange and red lines indicate
linear regression fits. See legend of Fig.
3 for number of tested flies and text for more explanations.
Values are means ± s.d.