Mid and Hind Legs Stabilize High-speed Turning

two beetles on branch in water during the day

Biological Strategy

Whirligig beetles

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Modify Position

Many resources that living systems require for survival and reproduction constantly change in quantity, quality, and location. The same is true of the threats that face living systems. As a result, living systems have strategies to maintain access to shifting resources and to avoid changing threats by adjusting their location or orientation. Some living systems modify their position by moving from one location to another. For those that can’t change location, such as trees, they modify position by shifting in place. An example of an organism that does both is the chameleon. This creature can move from place to place to find food or escape predators. But it also can stay in one place and rotate its eyes to provide a 360-degree view so that it can hunt without frightening its prey.

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Distribute Energy

Many forms of energy are naturally available, including kinetic, potential, thermal, elastic, radiant, chemical, and more. All living systems require energy to carry out their many activities. Energy isn’t a physical object that can be held, so it also can’t be pushed, pulled, or carried. However, it can be transmitted or transformed. For example, the golden-scale snail has a tri-layered shell that dissipates, or transfers, forces from a predator biting down on it, thereby minimizing damage to its soft body inside the shell.

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Move in/on Liquids

Water is not only the most abundant liquid on earth, but it’s vital to life–so it’s no surprise that the majority of life has evolved to thrive on and under its surface. Moving efficiently in and on this dense and dynamic substance presents unique challenges and opportunities for living systems. As a result, they have evolved countless solutions to optimize drag, utilize surface tension, fine tune buoyancy, and take advantage of various types of currents and fluid dynamics. For example, sharks can slide through water by reducing drag due to their streamlined shape and specially shaped features on their skin.

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Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

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The mid and hind legs of whirligig beetle stabilize turning while maintaining speed due to specialized lengths and points of attachment.

The whirligig beetle swims quickly atop water, yet it still excels in making sharp turns. This is due to a specialized leg structure that suggests the main role of its hind legs is propulsion. In contrast, the primary function of its middle legs is stability control, maintaining a given path during swimming.

The beetle’s hind legs are longer and have denser swimming hairs (called laminae) than its middle legs, providing the hind legs greater contact with the water that enables them to generate greater thrust. Additionally, the hind legs are attached lower on the beetle’s abdomen than its middle legs. This increases the distance between the beetle’s center of mass and the point at which the greatest force is generated against the water; in turn, the hind legs produce an increase in angular velocity, allowing the beetle to quickly change orientation in the water. To maintain a stable path, the middle legs balance out this angular velocity.

This strategy was contributed by Rachel Major

Last Updated September 14, 2016

References

Journal article

Experimental Studies and Dynamics Modeling Analysis of the Swimming and Diving of Whirligig Beetles (Coleoptera: Gyrinidae)

PLoS Comput Biol | 29/11/2012 | Zhonghua Xu, Scott C. Lenaghan, Benjamin E. Reese, Xinghua Jia, Mingjun Zhang |

Philip R. LeDuc

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