SUMMARYThermoregulation plays a key role in bee foraging, allowing some species to forage in suboptimal temperatures. Recently, bumble bee thoracic temperature (T th ) has been shown to increase with nectar carbohydrate content. However, pollen is also vital to bees and exhibits a greater than 20-fold range in protein quality. We provide the first demonstration that bee T th is also correlated with pollen quality. We allowed bumble bee, Bombus impatiens, foragers from two colonies to collect pollen varying in quality (25%, 50%, 75% and 100% by mass mixed with indigestible α-cellulose). We used infrared thermography to measure surface T th when a forager finished collecting feeder pollen and when she returned to the nest. Foragers significantly elevated their T th over ambient air temperature while collecting pollen and maintained this elevated T th upon returning to the nest. On average, foragers increased T th over ambient by 0.4°C per 25% increase in pollen protein content. Bumble bees can therefore adjust their thoracic temperature according to pollen quality.
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