Climate change heralds an era of increased heat waves, with global surface temperatures increasing faster since 1970 than in any other 50-year period in the last 2000 years [1]. By the mid-21st century, compound heat waves are projected to become more frequent, with 20–30 additional high heat days per year [2]. Emission restrictions under the Paris Agreement have thus far successfully reduced potential global warming by 2050 from 4°C to 2.1–2.8°C [3]. However, these rises are still expected to trigger multiple climactic points of no return [4]. We are hurtling toward a world defined by climactic extremes, and understanding the organismal impacts of high heat is increasingly urgent.

Insects, due to their short-generation times and their sensitive ecological requirements, offer a powerful model for studying rapid physiological and behavioral responses to high temperatures [5]. The most taxonomically diverse group of organisms on Earth, representing >90% of all animal species [6], insects also provide insight into climate-driven biodiversity shifts. However, terrestrial insect populations have declined by approximately 8.81% per decade between 1960 and 2005 [7], largely due to climate change, agrochemical use, and habitat loss.

Solitary insects primarily respond to temperature extremes by moving in space or time to remain in a constant environment or by exploiting phenotypic plasticity or evolutionary adaptation [8]. Social insects, however, possess an additional tool in mitigating thermal stress: cooperative group behavior. Here, we discuss how bumblebees (Bombus) in particular exemplify the ways in which eusocial living systems can buffer against environmental challenges. Bumblebees are broadly distributed across diverse climates, with greater than 250 species worldwide, making them an ideal model for studying evolutionary and plastic responses to temperature extremes. Like other eusocial insects, the division of labor within the colony enables bumblebees to efficiently allocate resources under stress. For example, some individuals may engage in active thermoregulation, while others continue foraging and brood care, preserving colony function and size despite environmental fluctuations (see Table 1 for definitions) [9]. However, unlike ants and honeybees, bumblebees lack the strict age-based division of labor. Instead, early life environmental conditions, including heat exposure and social experience during development, shape adult roles within the colony 10, 11, 12. We can therefore use adult behavioral measures as an outcome measure for early life environmental manipulations.

While previous studies have largely focused on bumblebee adaptations to cold temperatures 13, 14, 15, 16, 17, 18, far less is known about their responses/resilience to high temperatures. This is a critical gap in understanding: high heat imposes destabilizing effects on membranes and proteins, making it more difficult for insects to acclimate to heat than to cold 19, 20. At high temperature ranges of 40–55°C, for example, bumblebees reach their critical maximum temperature (CTmax) and begin to spasm before experiencing loss of muscle control 21, 22, 23, 24. Social bees are more resistant to heat and maintain their typical behaviors to a higher thermal limit than solitary bees [22]. However, formal studies of bumblebee thermal tolerance remain limited and heavily biased toward commercially available species, primarily Bombus impatiens and terrestris. These species exhibit a host of behavioral and physiological adaptations between CTmin and CTmax that likely buffer them against heat waves more effectively than solitary bees. In this review, we highlight how the behavioral repertoire of eusocial insects provides a uniquely suitable lens for studying the impact of climate change on dynamic societies. We focus on the urgent gap in understanding bumblebee responses to high heat and propose additional studies andanalytical frameworks to facilitate the identification of conserved behavioral and neural mechanisms to heat stress.