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Abstract Honeybees are master thermoregulators, capable of maintaining nest homeostasis across fluctuating ambient temperatures. When workers must cool their nest, they use multiple thermoregulatory behaviors (e.g., fanning, collecting water), but bearding, where hundreds to thousands of workers evacuate their nest and form a bivouac outside, is relatively unexplored. Here, we (1) describe natural bearding patterns, (2) experimentally manipulate colonies to determine what impacts beard size and timing, and (3) explore how workers dissipate back into their nest. We show that bearding occurs daily in hot weather, but the largest beards consistently happen in the evening/night, between the hours of 1800 and 2400. Beards are located around the nest entrance, but workers bias their position toward the shaded side of the nest box. As colony size increases, beard size and duration also increase, but the proportion of the colony bearding does not increase with colony size. Colonies with and without brood still cast beards; brood presence/absence did not impact beard size or duration. After noticing that beards tend to dissipate at sunrise, we experimentally showed that beards induced in the afternoon dissipate within 1–2 h, whereas beards induced in the evening remain overnight (10+ h). Bearding overnight, however, does carry risks for developing brood inside, as nest temperatures dropped below the optimal range, until the beard dissipated at sunrise. What cues workers use to depart the beard remain unknown, but experimentally illuminating colonies at night did not induce beards to dissipate. Our results suggest that bearding is an individual decision, not one that is coordinated across the colony. Still, these individual actions result in a dramatic collective response that colonies employ to reduce the temperature of their nest. Here, we show how and when colonies use bearding, despite its risks. 

Honey bees are renowned architects. The workers use expensive wax secretions to build their nests, which reach a mature, seemingly steady state, relatively quickly. After nest expansion is complete, workers do not tear down combs completely and begin anew, but there is the possibility they may make subtle changes like adding, removing, and repositioning existing wax. Previous work has focused on nest initiation and nest expansion, but here we focus on mature nests that have reached a steady-state. To investigate subtle changes to comb shape over time, we tracked six colonies from nest initiation through maturity (211 days), photographing their combs every 1–2 weeks. By aligning comb images over time, we show that workers continuously remove wax from the comb edges, thereby reducing total nest area over time. All six colonies trimmed comb edges, and 98.3% of combs were reduced (n = 59). Comb reduction began once workers stopped expanding their nests and continued throughout the experiment. The extent to which a comb was reduced did not correlate with its position within the nest, comb perimeter, or comb area. It is possible that workers use this removed wax as a reserve wax source, though this remains untested. These results show that the superorganism nest is not static; workers are constantly interacting with their nest, and altering it, even after nest expansion is complete. 

Form follows function throughout the development of an organism. This principle should apply beyond the organism to the nests they build, but empirical studies are lacking. Honeybees provide a uniquely suited system to study nest form and function throughout development because we can image the three-dimensional structure repeatedly and non-destructively. Here, we tracked nest-wide comb growth in six colonies over 45 days (control colonies) and found that colonies have a stereotypical process of development that maintains a spheroid nest shape. To experimentally test if nest structure is important for colony function, we shuffled the nests of an additional six colonies, weekly rearranging the comb positions and orientations (shuffled colonies). Surprisingly, we found no differences between control and shuffled colonies in multiple colony performance metrics—worker population, comb area, hive weight and nest temperature. However, using predictive modelling to examine how workers allocate comb to expand their nests, we show that shuffled colonies compensate for these disruptions by accounting for the three-dimensional structure to reconnect their nest. This suggests that nest architecture is more flexible than previously thought, and that superorganisms have mechanisms to compensate for drastic architectural perturbations and maintain colony function.