A set of incredible high-speed videos revealed jumping baby praying mantises can achieve ultra-precise landings without spinning out of control, contrary to previous belief.
The news videos proved the young insects actually harness this spinning motion, allowing them to jump accurately while at the same time repositioning their body in mid-air in less than a tenth of a second, the University of Cambridge reported. Until these observations, scientists had assumed most insects of this size could not control their jumps, often resulting in crash landings.
To make their findings, a team of researchers placed a thin black rod near a platform on which a mantis sat to be used as a jumping target. They observed that during the jumps, the mantises rotated their legs and abdomens at the same time, but in varying directions. This technique allowed the insects to reach their target with surprising accuracy at a speed faster than the blink of an eye. The analysis showed the mantises deliberately performed the controlled spin at the point of takeoff, then manipulated the angular momentum through limb rotations to reposition their bodies in mid-air and precisely hit their target.
"We had assumed spin was bad, but we were wrong - juvenile mantises deliberately create spin and harness it in mid-air to rotate their bodies to land on a target," said study author Professor Malcolm Burrows from Cambridge University's Department of Zoology. " As far as we can tell, these insects are controlling every step of the jump. There is no uncontrolled step followed by compensation, which is what we initially thought."
In the study, the scientists looked at a total of 381 slow motion videos of 58 baby mantises making the epic jump. The mantises proved to accurately hit the target almost every single time. When the target was moved closer, the insects were observed to spin themselves twice as fast to ensure their bodies were parallel when they hit it.
"The mantis gives itself an amount of angular momentum at take-off and then distributes this momentum while in mid-air: a certain amount in the front leg at one point; a certain amount in the abdomen at another - which both [stabilize] the body and shift its orientation, allowing it to reach the target at the right angle to grab on," said Gregory Sutton from Bristol University.
When the researchers restricted the insects' ability to harness the spread of the spin with their extremities by gluing segments of their body together, they were astonished to find the jump was not impeded. The mantises still accurately reached their target, but could not rotate their bodies into the correct position for landing, causing them to crash head-on and bounce off. In the future, the researchers hope to gain insight into how the insects accurately reach their targets at such high speeds.
"We can see the mantis performs a scanning movement with its head before a jump. Is it predicting everything in advance or does it make corrections at lightning speed as it goes through the jump? We don't know the answer between these extreme possibilities," Burrows said.
The findings could also help solve problems seen in robotics. Small robots often experience problems reaching their targets with the accuracy seen in these baby mantises, but the insects could be used as a model to improve their success rate.
"For small robots, flying is energetically expensive, and walking is slow. Jumping makes sense - but controlling the spin in jumping robots is an almost intractable problem. The juvenile mantis is a natural example of a mechanical set-up that could solve this," Sutton said.
The findings were published in a recent edition of the journal Current Biology.
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