Where Do Native Bees Go During a Heat Wave?

You step outside on the hottest day of the year and the flowers are still there, but the bees have vanished. So where did they go? The good news: they didn't die, and they didn't leave. This episode follows North America's native bees into their heat-wave hiding places and unpacks the five strategies they use to survive extreme heat. Kelly explains why bees shift their foraging to the cool bookends of the day, the hidden temperature ceiling — the critical thermal maximum — that's different for every species, the mid-flight "radiator" trick bumblebees use to dump excess heat, and why the underground tunnels of solitary mining bees are one of nature's best passive air conditioners. Plus a genuinely surprising twist: for at least one desert bee, the thing that ends its flying day isn't the heat at all — it's running out of water. It's not a crisis story. It's a story about how astonishingly well-built these bees already are.

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KEY SOURCES & DOIs

Behavioral thermoregulation & activity timing

• • Chappell, M.A. (1982). Temperature regulation of carpenter bees (Xylocopa californica) foraging in the Colorado Desert of Southern California. Physiological Zoology 55(3): 267–280. DOI: 10.1086/physzool.55.3.30157890
  • Harrison, J.F. et al. (2023). Recent advances in insect thermoregulation. Journal of Experimental Biology 226(18): jeb245751. DOI: 10.1242/jeb.245751

Critical thermal maximum & species variation

• • Hamblin, A.L., Youngsteadt, E., López-Uribe, M.M., & Frank, S.D. (2017). Physiological thermal limits predict differential responses of bees to urban heat-island effects. Biology Letters 13(6): 20170125. DOI: 10.1098/rsbl.2017.0125
  • Hamblin, A.L., Youngsteadt, E., & Frank, S.D. (2018). Physiological and biochemical responses of bees to urbanization. Scientific Reports 8: 3868. DOI: 10.1038/s41598-018-38338-0

Bumblebee heat exchange (thorax/abdomen)

• • Heinrich, B. (1976). Heat exchange in relation to blood flow between thorax and abdomen in bumblebees. Journal of Experimental Biology 64(3): 561–585. DOI: 10.1242/jeb.64.3.561
  • Sepúlveda-Rodríguez, G., Roberts, K.T., Araújo, P., Lehmann, P., & Baird, E. (2024). Bumblebee thermoregulation at increasing temperatures is affected by behavioral state. Journal of Thermal Biology 121: 103830. DOI: 10.1016/j.jtherbio.2024.103830

Underground nest microclimate

• • Antoine, C.M., & Forrest, J.R.K. (2021). Nesting habitat of ground-nesting bees: a review. Ecological Entomology 46(2): 143–159. DOI: 10.1111/een.12986
  • Cane, J.H., & Neff, J.L. (2011). Predicted fates of ground-nesting bees in soil heated by wildfire: Thermal tolerances of life stages and a survey of nesting depths. Biological Conservation 144(11): 2631–2636. DOI: 10.1016/j.biocon.2011.07.019

Water loss as the activity limit

• • Johnson, M.G., Glass, J.R., & Harrison, J.F. (2023). Water loss, not overheating, limits the activity period of an endothermic Sonoran Desert bee. Functional Ecology 37(12): 3060–3072. DOI: 10.1111/1365-2435.14438
  • Johnson, M.G., Glass, J.R., & Harrison, J.F. (2022). A desert bee thermoregulates with an abdominal convector during flight. Journal of Experimental Biology 225(19): jeb244147. DOI: 10.1242/jeb.244147

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