Thermoregulation in Bumblebee Colonies. II. Behavioral and Demographic Variation throughout the Colony Cycle

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Abstract
Colonies founded by wild-caught queens were reared at either 15 C with or without an insulated nest or at 25 C for the duration of the colony cycle. Brood-maintenance and brood-incubation behaviors, brood ( ) and nest-chamber ( ) temperatures, and the number of bees produced were monitored. The total number of foragers was relatively fixed in young colonies. The occurrence of brood incubation varied inversely with population size and was highest at low ambient temperature ( ). In contrast, the occurrence of brood maintenance varied directly with population and was highest at high . All colonies had produced their maximum number of workers and started producing reproductives at 9-10 wk after the emergence of the first workers of the colony. The numbers of bees produced per colony at 15 C with insulation and at 25 C were similar. Uninsulated colonies at 15 C produced fewer bees and maintained lower . These findings suggest that low may limit population growth but has no apparent effect on the timing of events during the colony life cycle.