Insects are the most diverse species on our planet, numbering more than five million different types, and have exploited nearly every terrestrial and many aquatic and aerial niches. Social insects, those that form cooperative societies with specialized castes based on division of labor, for example, afford spectacular examples of collective behavior in such instances as termite mounds, locust swarms and bee clusters and hives. These collective architectures are functional and allow the organisms to maintain a relatively uniform micro-environment even with a variable macro-environment. Understanding how this is achieved in a variety of climates and environments is not just a problem in ecology or physiology, but also one in physics, given that they exchange information, energy and matter continually with the environment. The study looks at the collective dynamics of bee colonies that maintain their temperature in a closed environment using active ventilation driven by fanning, and the structural dynamics of actively adherent bee clusters that can respond to vibrotactile stimuli by changing their shape. While current studies in active matter primarily focus on the patterns in space and time that result from interactions, the new experimental and theoretical approaches will focus on how active systems can perform functions by coupling form, flows and forces in the presence of feedback. Organisms live in varying environments and must therefore be able to tolerate variations in the macro-environment they inhabit. They do this by creating niches that damp out the large scale variations without completely isolating themselves. Outside human societies, nowhere is this better seen than in social insects. The current study takes a quantitative physical approach to the problem, building on the empirical information obtained by biologists. It aims to partially break down the artificial barrier between physics and biology, i.e. between non-living and living matter by showing how living matter shapes itself and its physical non-living environment to achieve function. By synthesizing aspects of hydrodynamics, statistical mechanics and decision making for active matter systems, the research will thus have impact on a range of biological and engineered systems where behavior and decision making come together with flows and forces.
The collective behavior of the organisms creates environmental micro-niches that buffer them from environmental fluctuations e.g. temperature, humidity, mechanical perturbations etc., thus coupling organismal physiology, environmental physics and population ecology. The current study proposes to use a combination of biological experiments, theory, computation and robotic biomimicry to understand how a collective of bees can integrate physical and behavioral cues to attain a non-equilibrium steady state that allows them to resist and respond to environmental fluctuations of forces and flows. The researchers will analyze how bee clusters change their shape and connectivity and gain stability by spread-eagling themselves in response to mechanical perturbations, using a combination of optical and x-ray imaging techniques. Similarly, the researchers will study how bees in a colony respond to environmental thermal perturbations by deploying a fanning strategy at the entrance that they use to create a forced ventilation stream that allows the bees to collectively maintain a constant hive temperature. When combined with quantitative analysis and computations in both systems, the researchers will integrate the sensing of the environmental cues (acceleration, temperature, flow) and convert them to behavioral outputs that allow the swarms to achieve a dynamic homeostasis, that will be tested using collective robotics using simple agents that can sense each other, their environment and move in response to both cues.
