Appendages Correct Falling Posture

Biological Strategy

Pea aphid

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Manage Impact

An impact is a high force or mechanical shock that happens over a short period of time, such as a hammer hitting a nail rather than a hand pushing slowly against a wall. Because of their speed and force, impacts don’t allow materials to slowly adjust to the force, which can lead to cracks, ruptures, and complete breakage. Therefore, living systems have strategies that can absorb, dissipate, or otherwise survive that force without the need to add large amounts of material. For example, the Toco toucan’s large beak is very lightweight, yet can withstand impacts because it’s made of a composite material with rigid foam inside and layers of a hard, fibrous material outside.

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Adapt Behaviors

The environment is constantly changing, and if living systems can’t adapt to these changes, they don’t survive. Environmental changes can be cyclic such as seasons, sudden such as floods or forest fires, or gradual but long-term, such as ecosystems shifting from early to mature stages. These changes require some flexibility in behavioral responses to match the specific conditions. For example, as a fish called the lamprey swims, it constantly faces changes in currents. Skin sensors help it detect those changes and adjust its motion accordingly.

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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 appendages of the pea aphid correct falling posture by strategically moving to an aerodynamically unstable position.

When a pea aphid falls off a leaf, it almost always falls belly-side up. In order to land on its feet, the aphid moves its antennae up and forward and its hind and mid legs back towards the body.

This appendage orientation creates a body position that increases drag through added air resistance on the aphid. When something is falling, it naturally moves to an orientation with the least amount of resistance. Given this, the strategic positioning of the antennae and legs creates unnatural stress and needs to be corrected. By purposefully increasing air resistance when falling, the aphid’s body automatically shifts to the the optimal orientation; in this case, belly-side down.

This strategy was contributed by Rachel Major

Last Updated August 23, 2016

References

Journal article

Adaptive aerial righting during the escape dropping of wingless pea aphids

Current Biology | 04/02/2013 | Gal Ribak, Moshe Gish, Daniel Weihs, Moshe Inbar

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