Video: How praying mantises leap accurately
If there was ever an animal version of the Olympics, the long jump would have to feature. Lizards rely on their tails for accurate leaping, and apes on using their legs in various ways. But praying mantises use a different trick altogether, as revealed by painstaking analysis of almost 400 videos of young mantises leaping onto a nearby vertical pole.
To ensure a smooth but accurate journey through the air, mantises balance out twists and rotations in three parts of their bodies: their abdomens, their front “grasping” legs, and their hind “standing” legs.
The counter-directions of the two sets of legs, for example, provide the overall balance of forces to keep the trunk in line with the landing target.
“One pair goes anticlockwise and the other clockwise, and they switch motion several times throughout the entire manoeuvre,” says Malcolm Burrows of the University of Cambridge. “It means the central trunk is kept stable throughout and correctly orientated to landing on the target.”
The entire jump, from when the mantis eyes the target and curls its abdomen in preparation for leaping until it lands, lasts just a tenth of a second. The leap involves four major exchanges of rotational forces between the three rotating body parts. “It’s an incredibly complicated thing to do in just 100 milliseconds,” says Burrows.
To confirm that the twisting abdomen is indispensable for the manoeuvre, Burrows used glue to prevent the insects from flexing it during their leaps. The glue – although superglue – doesn’t stick well to the waxy cuticles of insects and soon rubbed off. Sure enough, these insects failed to reach their target properly, colliding with it head first instead.
“They couldn’t generate enough spin, and so nutted the target instead,” says Burrows, who points out that unlike winged adults, young mantises like those studied lack wings and so must rely on leaping around in bushes and grass to move around and find the best places to catch prey. He says that the insights gained could be useful for designing small robots that can jump.
Journal reference: Current Biology, DOI:10.1016/j.cub.2015.01.054
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