Fig. 1

Design of the brood-swap experiment. For each biological replicate, a large source colony in the brood care phase was used to establish two colonies of 250 1-month-old workers and 100 marked ≥ 3-month-old workers. One of these colonies received approximately 250 larvae. After a full colony cycle, each colony contained a complete cohort of brood and workers and was in either peak brood care phase (with larvae) or early reproductive phase (with eggs and pupae). On the day the first eggs were laid, the 1-month-old workers were subdivided in colonies of 45 workers each. One colony from each phase served as the control colony and was given brood from the mother colony. The remaining colonies received brood from the mother colony in the opposite phase of the cycle, triggering the transition toward the alternative phase. Colonies were subsequently collected 6, 12, 24, 48, or 96 h post treatment. BR workers transitioning from the brood care phase to the reproductive phase (after larvae were removed and pupae added), RB workers transitioning from the reproductive phase to the brood care phase (after pupae and eggs were removed and larvae added), BC workers from the brood care phase with larvae (brood care phase control), RC workers from the reproductive phase with pupae (reproductive phase control)