Figure 4. Mean weight (g) (± SE) of Bombus impatiens colonies by observation day (days on which colonies were weighed).

Colonies were initially confined to flowering field plots of buckwheat (n = 10), red clover (n = 9), or purple tansy (n = 10) in the field. After 16 days in the field, which included four observation days, colonies were brought to the lab and maintained in a growth cabinet until two weeks after the first emergence of a new queen.