Legs Synchronize During Jumps

a brown insect with large eyes sits in a red object with yellow pollen stuck to its body with a blurry background

Biological Strategy

Planthopper

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Living systems must move through gases (which are less dense than liquids and solids) such as those in the earth’s atmosphere. The greatest challenge of moving in gases is that because the living system is heavier than the gas, it must overcome the force of gravity. Moving efficiently in this light medium presents unique challenges and opportunities for living systems. As a result, they have evolved countless solutions to optimize drag and increase lift so that they can stay aloft and take advantage of variable currents. Additionally, they must overcome gravity when moving from a liquid or solid into the air. The fairyfly, the smallest known insect, is a tiny wasp that must move through the air. To the wasp, air feels like a heavy liquid and to move through it, it uses special feathery oars rather than wings.

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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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Hind legs of planthoppers produce powerful synchronized jumps thanks to a mechanical linkage.

Learn more about the mechanical functioning of the legs of the planthopper Issus coleoptratus in Tom McKeag’s case study, “Gearing Up (and away): How a little backyard bug might change engineering” on page 10 of Zygote Quarterly:

“The hind legs of Issus (Hemiptera, Issidae) move in the sameplane underneath the body, an arrangement that means they mustalso move synchronously to power jumping. Moreover, they moveso quickly that energy must be stored before a jump and thenreleased suddenly. High speed imaging and analysis of the mechanicsof the proximal joints of the hind legs show that mechanicalmechanisms ensure both synchrony of movements and energy storage…Synchrony is achieved by mechanical interactionsbetween small protrusions from each trochantera…which touch at the midline when the legs are cocked beforea jump. In dead Issus, a depression force applied to a cockedhind leg, or to the tendon of its trochanteral depressor musclecauses a simultaneous depression of both hind legs. The protrusionof the hind leg that moves first nudges the other hind leg sothat both move synchronously. Contractions of the trochanteraldepressor muscles that precede a jump bend the metathoracicpleural arches of the internal skeleton. Large areas of thesebow-shaped structures fluoresce bright blue in ultraviolet light,and the intensity of this fluorescence depends on the pH ofthe bathing saline. These are key signatures of the rubber-likeprotein resilin. The remainder of a pleural arch consists ofstiff cuticle. Bending these composite structures stores energyand their recoil powers jumping.” (Burrows 2009:469)

http://jeb.biologists.org/cgi/content/abstract/213/3/469?ijkey=60c39c53fc6b54e21f259e752d22069fe0522414&keytype2=tf_ipsecsha

Last Updated November 3, 2020

References

Journal article

Energy storage and synchronisation of hind leg movements during jumping in planthopper insects (Hemiptera, Issidae)

Journal of Experimental Biology | 19/01/2010 | M. Burrows

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