Fig. 1. Size and division of labor in B. terrestris. (A) The relationship between body size (forewing length) and the propensity to forage. Each filled circle represents a single bee observed in Session A of Colony 2. The broken line depicts the regression of foraging propensity on wing length (y=0.16x–1.18, R²=0.46). Similar results were obtained in Session B for this colony and in both sessions for Colony 3 (size was not recorded in Colony 1). (B) Age-related plasticity in worker task. Individually marked workers were observed for two sessions of 4 successive days each. The two sessions (A and B) were separated by a period of 3–4 days. The figure depicts the percentage of foragers (filled bars), intermediate (hatched bars), and nurses (open bars) in session B as a function of their task in session A. Data were pooled from the three colonies. Numbers within bars indicate sample size. (C) Body size and age at first pollen foraging. Foraging trips (a bee returning to the hive with pollen) of individually marked bees were recorded using an automatic video system equipped with motion detection technology. Large bees (marginal cell 2.75 mm; dotted line, N=59) began to forage at a younger age than small bees (marginal cell <2.75 mm; continuous line, N=34; Kaplan–Meier Survival Analysis with Breslow statistics, P=0.007).