Fig. 4. Relationship between CO₂ release and running speed. Data are shown for the five different slopes of the respirometric chamber examined: (A) -60° (steep descent), (B) -30°, (C) horizontal, (D) 30°, and (E) 60° (steep ascent). See also inset sketches. Red data points in C give mean values obtained from all five inclines. Black lines represent linear fit regressions to the data up to 90 mm s^-1 speed (A) y=1.64+9.7x10^-3x, r²=0.71; (B) y=1.73+10.5x10^-3x, r²=0.88; (C) y=1.50+11.4x10^-3x, r²=0.91; (D) y=1.55+10.1x10^-3x, r²=0.94; (E) y=1.37+13.0x10^-3x, r²=0.82. Numbers of ants in the speed bins were 26 in each of the 6 lower bins (0-5 mm s^-1 to 45-55 mm s^-1), 25 (55-65 mm s^-1), 25 (65-75 mm s^-1), 24 (75-85 mm s^-1), 22 (85-95 mm s^-1), 18 (95-105 mm s^-1), 12 (105-115 mm s^-1) and 7 (115-125 mm s^-1). Estimates for resting metabolic rates of intact (a) and decapitated (b) ants are indicated as blue dotted lines. The speed range up to 90 mms^-1 is shaded (see Discussion for explanation). Values are means ± S.D.