Fig. 4. Feeding time (min) (A), crop load (mg) (B), and metabolic rates of foraging ants (µW) (C) as a function of three different flow rates (0.236, 1.18 and 2.36 µl min^–1) and three different sugar solution concentrations (1, 5 and 30%). Values are means ± s.e.m. (N=6–17). Posteriori (Tukey test after first two-way ANOVA): a,b, P<0.01; a,c, P<0.001; same letters do not differ significantly. Posteriori (Tukey test after second two-way ANOVA: analysis differences between all concentration of 0.236 and 1.18 µl min^–1, i.e. we did not take into account the 2.36 µl min^–1 groups): for (A) 0.236 µl min^–1 and 1% vs 0.236 µl min^–1 and 5% or 30% (P<0.001), 0.236 µl min^–1 and 5% or 30% vs 1.18 µl min^–1 and 1% (P<0.001); for (B) 0.236 µl min^–1 and 1% vs 1.18 µl min^–1 and 5% or 30% (P<0.001), 1.18 µl min^–1 and 1% vs 1.18 µl min^–1 and 30% (P<0.001); for (C) 0.236 µl min^–1 and 1% vs 1.18 and 30% (P<0.05).