Abstract
Whirligig beetles (Coleoptera, Gyrinidae) can fly through the air, swiftly swim on the surface of water, and quickly dive across the air-water interface. The propulsive efficiency of the species is believed to be one of the highest measured for a thrust generating apparatus within the animal kingdom. The goals of this research were to understand the distinctive biological mechanisms that allow the beetles to swim and dive, while searching for potential bio-inspired robotics applications. Through static and dynamic measurements obtained using a combination of microscopy and high-speed imaging, parameters associated with the morphology and beating kinematics of the whirligig beetle's legs in swimming and diving were obtained. Using data obtained from these experiments, dynamics models of both swimming and diving were developed. Through analysis of simulations conducted using these models it was possible to determine several key principles associated with the swimming and diving processes. First, we determined that curved swimming trajectories were more energy efficient than linear trajectories, which explains why they are more often observed in nature. Second, we concluded that the hind legs were able to propel the beetle farther than the middle legs, and also that the hind legs were able to generate a larger angular velocity than the middle legs. However, analysis of circular swimming trajectories showed that the middle legs were important in maintaining stable trajectories, and thus were necessary for steering. Finally, we discovered that in order for the beetle to transition from swimming to diving, the legs must change the plane in which they beat, which provides the force required to alter the tilt angle of the body necessary to break the surface tension of water. We have further examined how the principles learned from this study may be applied to the design of bio-inspired swimming/diving robots.
Highlights
Few organisms maintain the ability to freely crawl on land, swim in water, and fly through the air; the whirligig beetle (Coleoptera Gyrinidae) is able to efficiently maneuver in all three environments [1]
By integrating experimental studies and theoretical analysis, this research has made several contributions to the study of dynamics and kinematics involved in the swimming and diving of whirligig beetles with potential applications in bio-inspired robotics
Results from the swimming dynamics model demonstrated that the most efficient strategy for net forward motion was the beating of the hind legs simultaneously
Summary
Few organisms maintain the ability to freely crawl on land, swim in water, and fly through the air; the whirligig beetle (Coleoptera Gyrinidae) is able to efficiently maneuver in all three environments [1]. The whirligig beetle has the fastest measured speed for a swimming insect, while still maintaining the ability to produce very sharp turns. We will focus on investigating how the whirligig beetle uses its legs to swim on the surface of water, and how it transitions from surface swimming to diving. While many studies have attempted to understand the highly efficient swimming motion of whirligig beetles [2,3,4], few studies have investigated the swimming mechanism and the transition to diving. Parameters related to swimming and diving of the whirligig beetle were characterized through experimental analysis, and further used to conduct simulations to answer questions that could not be experimentally verified
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