Figure 2. Energetics and thermoregulation of honeybees foraging sucrose in shade (grey/filled symbols) and in sunshine (yellow/open symbols).

One symbol represents one mean per stay (N = 217 stays in shade and 183 in sunshine; 20 bees). (A) CO₂ production rate (VCO₂), (B) body surface temperature of head (T_hd), thorax (T_th) and abdomen (T_ab), (C) duration of stay, (D) costs per stay, and environmental parameters were measured simultaneously in all individuals. Dashed-dotted line in (B): isoline. T_a = ambient air temperature near the bees in the measurement chamber, T_outside = temperature in shade outside the measurement chamber, T_s = sucrose temperature. Regression lines (all P<<0.0001, ANOVA): (A, B) cubic (y = A+B*x+C*x²+ D*x³); (C, D) exponential decay (y = A1*e^{(−x/t1)+y0)}), for constants and statistics see Table 1. Inserts: if not given, axes labelings as in main graphs; insert in (C): T_a, T_s, T_ab, T_hd, T_th refer to x-axis temperature to be used, respectively.