Colony size
We used the number of adult bees to represent the colony size, like previous studies on other eusocial bees (Dornhaus et al. 2012). To count the number of adult bees in individual colonies, hives were closed at night on the day prior to the experiment using a fine metal gauze (5 x 10 cm) to cover hive entrances, which prevented adult bees from leaving the colony while allowing adequate ventilation. The following day, hives were transferred to a small laboratory and enclosed in a 1.5 x 1 m fine mesh cage to aid collection of adult bees using a manual aspirator. For the more populous species (F. longipes and S. aff. postica ), carbon dioxide (glass cylinder, 95% concentration) was given to the colony for up to two minutes to anesthetize the individuals (Tustain and Faulke 1979) prior to their capture. Males and female workers were not discriminated during counting, while the mated queen and the gynes were counted and separated from other adult bees. At the end of the bee counting, all brood combs, food pots and adult bees were carefully returned to the hive and colonies received supplemental food (sugar syrup and pollen) to aid their recovery post assessment. By following these procedures, no colonies died due to our handling.