A Swarm of Bee Research

Bees are amazing little creatures; while some of them live solitary lifestyles, many bee species form large colonies, or hives, and function as a superorganism. Scientific interest in bees covers many different angles. Some researchers are interested in how bees learn and communicate as part of the superorganism. Others study how bees fly and recognize objects during flight— skills that have intriguing implications for development of manmade drones. And, as we are all sadly aware, there is intense research on bee pathogens and the contribution of those pathogens to colony collapse. In this Open Highlights article, I will discuss some of the recent advances in our understanding of these fascinating insects. While one bee is small, a colony is mighty, and colonies are capable of extremely complex behaviors. How bees communicate and pass on knowledge has interested researchers for decades. In a recent paper in PLOS Biology [1], the authors demonstrate that bees are capable of social learning and cultural transmission—a first for invertebrates. In the study, the authors trained bees to perform a non-natural task: pulling a string to receive a sugar reward (Fig 1). The trained bees were then able to teach their colony-mates this string-pulling trick. Using a semi-natural colony simulation, they showed that the foraging bees learned the task, either from the trained bee or other learners (and very occasionally spontaneously), and that this behavior persisted even after the teacher was removed. This work demonstrates that bees can learn from watching other bees, and that this acquired skill can be spread and develop into a cultural element of the colony. Bees can be trained in other non-natural tasks, and a PLOS ONE paper unearths new insights into learning and memory by developing an operant conditioning test whereby bees push a cap to uncover a food source [2]. Bee learning is also studied in more natural setting as well; the Asian species of honey bee Apis cerana is often attacked by hornets (Vespa velutina), and authors of another PLOS ONE paper [3] find that the presence of predator odor or alarm pheromone (a chemical signal secreted by bees as a warning to their conspecifics) compromises the bees’ ability to associate a stimulus with a sugar reward. In addition to alarm pheromone, bees have evolved other mechanisms to warn their nestmates of danger. In a second PLOS Biology article [4], the authors show that Apis cerana can not only warn nest-mates of a predator, but can tell them how big a threat the colony is facing. The ‘stop signal’ identified by the authors is a brief vibrational pulse that informs the nest of the level and context of the danger (is there a large hornet at the front door, or a small hornet at a distant food source?). Bees receiving these signals behave differently, either avoiding a food source, remaining in the nest, or attacking the invading hornet by forming a ball of bees that kills the attacker by heating it to death. Communication within bee colonies is extremely complex. One of the primary mechanisms is through the famous “waggle dance,” which occurs on the dance floor as a means of signal amplification. But bees also engage in other types of collective behavior. In another PLOS ONE article, the authors provide evidence that Asian giant honeybees (Apis dorsata) engage in collective respiratory behavior to ventilate their hives for thermoregulation and freshness [5].