Xu Z, Lenaghan SC, Reese BE, Jia X, Zhang M. Experimental studies and dynamics modeling analysis of the swimming and diving of whirligig beetles (Coleoptera: Gyrinidae).
PLoS Comput Biol 2012;
8:e1002792. [PMID:
23209398 PMCID:
PMC3510063 DOI:
10.1371/journal.pcbi.1002792]
[Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Accepted: 10/05/2012] [Indexed: 11/18/2022] Open
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.
The whirligig beetles belong to the family Gyrinidae, consisting of over 700 species of water beetles. They are characterized by a divided eye, ellipsoidal body, and rapidly swim in circles when alarmed. Perhaps the most interesting characteristic of whirligig beetles is their ability to rapidly swim on the surface of water, and also to quickly transition to diving beneath the surface. In this study, we have measured the key physical parameters that allow whirligig beetles to swim and dive, and have used these values to develop dynamics models of the swimming and diving processes. Based on these models, we were able to analyze how the beetle is capable of making sharp turns, the efficiency of varying leg beating patterns, and the key parameters involved in swimming, as well as diving. We were then able to identify fundamental principles used by the beetle to transition from swimming to diving, and examine how the morphology and “design” of the beetle leads to its ability to rapidly swim and maneuver. Based on the results obtained, we further identified principles and components of the beetle design that could be translated into the development of bio-inspired robotics.
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