Abstract: To survive in noisy environments, organisms must buffer themselves against large fluctuations and accommodate adaptation over a wide range of length and time scales. In this context, organisms could be conceptualized as active matter where tension between order and disorder prevails: while ordered systems are stable and predictable, they leave little room for exploration; therefore, optimal functioning is often accomplished at an intermediate level of disorder. Examples include intrinsically disordered protein assemblies that remain intact under varying external mechanical and chemical stimuli, beetles that navigate using volatile celestial cues, and honeybee clusters that change their morphology to both regulate their bulk temperature, and to withstand mechanical stresses. In this talk I will focus on the latter example in which honeybees form swarms that take on an inverted cone shape. The bees hold on to each other, and form a large structure that can be hundreds of times the size of a single organism. The mechanism by which a multitude of bees work together, without an overseer, to create a stable structure that defies static gravity and dynamic stimuli (e.g. wind), remains elusive. To test the role of mechanical cues in the swarm morphogenesis, we developed an experimental setup in which mechanical perturbations were applied to a swarm. In response, the bees tuned the aspect ratio of the swarm dynamically toward a wider, more stable, cone. Disorder in this system is manifested in the ability of bees to sample their local environment and respond to events of sharp force by moving within the swarm, equivalent to a solid-liquid phase transition. Indeed, agent-based simulations where individual bees are capable of sensing local mechanical stresses, and respond by changing the global shape of the swarm, are in qualitative agreement with the experimental results. Together these observations suggest a new paradigm for sensing and feedback-driven stabilization of structures made of active elements.
This talk will stream live from SFIs YouTube channel.