A new study published in the journal Current Biology reveals that, unlike other jumping insects, wingless baby mantises don’t spin out of control when airborne. In fact, they both create and control angular momentum at extraordinary speeds to orient their bodies for precise landings.
The smaller you are, the harder it is not to spin out of control when you jump. Miniscule errors in propulsive force relative to the center of mass results in most jumping insects – such as fleas, leafhoppers and grasshoppers – spinning uncontrollably when they jump.
Until now, scientists worked under the hypothesis that such insects can’t control this, and spin unpredictably with frequent crash landings.
But new video analysis of the jumps of juvenile praying mantises has revealed a technique which actually harnesses the spinning motion, enabling them to jump with accuracy at the same time as repositioning their body mid-air to match the intended target – all in under a tenth of a second.
For this study, Prof Malcolm Burrows of Cambridge University and his colleagues analyzed a total of 381 slowed-down videos of 58 young mantises jumping to the target, allowing them to work out the intricate mechanics used to land the right way up and on target virtually every time.
“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,” Prof Burrows said.
“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 fact, when the scientists moved the target closer, the mantises spun themselves twice as fast to ensure they got their bodies parallel with the target when they grasped it.
They tested what would happen if they restricted the ability of the mantis to harness and spread the ‘spin’ to its extremities during a jump.
To do this, they glued the segments of the abdomen together, expecting the mantis to spin out of control.
Intriguingly, the accuracy of the jump wasn’t impeded. The mantises still reached the target, but couldn’t rotate their bodies into the correct position – so crashed headlong into it and bounced off again.
Another question for the team is to understand how the mantis achieves its mid-air acrobatics at such extraordinary speeds.
Prof Burrows said: “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.”
Malcolm Burrows et al. Mantises Exchange Angular Momentum between Three Rotating Body Parts to Jump Precisely to Targets. Current Biology, published online March 5, 2015; doi: 10.1016/j.cub.2015.01.054
This article was first published by Sci-News.com on 05 Mar 2015.