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Member Symposium

Plant-Insect Ecosystems

Physiology, Biochemistry, and Toxicology

Ecophysiology of Social Insects

Colonial thermoregulation and its limits during heat waves for honey bees

Wednesday, November 12, 2025
9:35 AM - 9:50 AM Pacific
Location: Oregon Convention Center, Portland Ballroom 251, OCC
Oral Presentation

We lack an understanding of the upper limits and mechanisms of colonial thermoregulation in the heat for honey bees and other pollinating insects. We experimentally exposed colonies to air temperatures of 52°C for 4.5 hours. Thermal stability of the brood center was 84%, with brood temperatures reaching known damaging 38°C in most colonies. Heat buffering mechanisms were heat storage in honey (40 watts), and in bees (3 watts), metabolic suppression (1.7 watts) and increased evaporative heat loss (0.7 watts). Colonies allow hive temperatures to fall below those optimal for brood development at night, increasing the capacity for passive thermal buffering to limit exposure to heat damage. Our data suggest that exposures to air temperatures over 50°C for multiple hours will be damaging for honey bee colonies. To assess the effects of longer-term, milder conditions, we monitored the growth and internal temperatures of nine colonies biweekly for three months during an Arizona summer.  Average temperatures in the brood center and edge were stable and within the optimal range of 34-36°C necessary for healthy brood development throughout the summer.  However, all hive locations exhibited cyclic, diurnal thermal fluctuations, and brood experienced considerable portions of each day above and below the optimal temperature range. Maximal air temperatures averaging 41°C over two weeks led to declines in colony population. Colonial thermoregulation fails to prevent negative impacts to populations during current and predicted heat waves in honey bees. Passive heat buffering mechanisms are very important and potential targets for heat mitigation.