CLICK AND RUN: INVESTIGATION OF CLICK BEETLES' ULTRAFAST CLICKING BEHAVIOR AS A MECHANISM FOR ESCAPE FROM CONSTRAINTS

Click beetles (Coleoptera: Elateridae) have evolved a unique clicking mechanism that enables them to rapidly convert stored elastic potential energy into kinetic energy. However, the biological reason for why this mechanism evolved remains unclear. Several hypotheses have been proposed, such as self-righting, jumping away from threats, or deterring predators. We focused on studying the functionality of clicking as a means of escaping constraints. To investigate how the clicking mechanism influences interactions with the surrounding environment, we created a 3-dimensional dynamic simulation model. This model simplifies the beetle's structure into several robotic components, including links, revolute joints, and torsional springs. We observed its response over time under various initial conditions and parameters, considering both prescribed and free joint movement. The simulation model showed that when fully constrained, forward and backward movement - and eventual escape - typically required multiple clicks. In contrast, in scenarios involving partial constraint, a single click frequently resulted in successful disengagement. This suggests that clicking plays a more important role in escaping partial constraints than in overcoming full confinement. The number of clicks required for escape was influenced by parameters such as surface stiffness and clamping force. We designed and fabricated a test rig that enabled precise constraint of live beetles in controlled orientations to replicate ecologically relevant postures encountered in natural environments. This setup allowed us to study the clicking behavior when constrained, through direct observation and kinematic analysis. We found that when fully constrained, click beetles cannot use the clicking mechanism to create enough lateral movement to escape the 4-sided constraint. However, when only partially constrained, the mechanism helps the click beetle break free. The combination of simulation and live beetle experiments enabled a more detailed investigation into the forces exerted during the click beetle's clicking motion and its impact on surrounding materials. This research provides further insights into the design and construction of legless robotic mechanisms capable of locomotion across diverse terrain (bio-inspired design) while also helping to answer evolutionary questions in biology (engineering-informed biology).