How mantis control their leaps.

By Dave Armstrong - 05 Mar 2015 20:5:0 GMT
How mantis control their leaps.

Ready, Steady, Go! The mantis nymph curls up its abdomen and then jumps so precisely that a target is never missed. At least during an experiment, the praying mantis has shone as a prime vaulter, enabling it to catch prey when its main armament, those powerful front legs are shorter than in the ferocious adult. There are also predator-escape possibilities when your leaps are so accurate.Nymph image; Credit: © Shutterstock

They push into the air with their legs and launch their bodies with a controlled spin, into the air. They rotate limbs and abdomen independently in order to sail through the air keeping their bodies level and directly parallel to the target. No, this is not a study of pole vaulters. This is one of the more primitive jumping creatures, the praying mantis. The insect has entranced humans from time immemorial and it has a primitive insect life history. But there is nothing simple about the vision, the behaviour and the cunning adaptations many species have made to the predation and trapping of their prey in every possible habitat.

The thing is, insects don’t have accurate jumping abilities normally whether they are the familiar flea or the least known microfauna of some forest. The only one to jump like this is the mantis. Malcolm Burrows and Gregory P Sutton of the Universities of Cambridge and Bristol in the UK have investigated jumping insects such as how mole crickets jump out of water. Here they wrote their paper with Darron A.Cullen of KU Leuven in Belgium and Marina Dorosenko in the journal, Current Biology, as Mantises Exchange Angular Momentum between Three Rotating Body Parts to Jump Precisely to Targets.

The juggling of their angular momentum is the scientific clue to the exclusivity of this discovery. What this means to robot manufacturers could be revolutionary. Whatever the intelligence involved, the mantis has a remarkably small space for its memory and coordination neurons. The robot that could use similar technologies would be one of the greatest advances we yet have. The centre of mass (COM) can be adjusted to control that primary spin, while 3 body parts are rotated to adjust it. The poor animal can be made to crash land by restricting any of these rotational movements.

Clever animals use many methods to control the great amounts of torque generated during takeoff. Geckos are excellent at jumping, using their tails to control the pitch, while Anolis lizards can alter direction with their tail. Cats are famous for rotating their body so as to land on their feet. The mantis, however, is jumping horizontally over a short distance, almost in a gliding behaviour pattern. The mantis of course also flies, as an adult, so we can assume the same abilities are used in landing and takeoff then. Comparing them with flying insects and many others can discover nothing like the accuracy of this precise jump. Almost all other insects completely lose control once they have left the ground and can often be observed in their frequent crashes to the ground, from the ants to true bugs and aphids. The zebra spiders are the only invertebrate that would seem able to repeat the feat!

The way in which mantis species target their jumps using many trajectories, as desired, is intriguing. It was 58 juvenile mantis that were used in these experiments, using rapid jumps lasting only 100 milliseconds. They swayed their large heads from side to side, scanning and getting a perspective, then curled their abdomen and leapt towards a thin black rod. This was their only target, as 400 leaps were made. In nature, they would have to consider wind direction and moving prey or even predators, but these small animals have technique and expertise in their repertoire. If you want to examine other species (this is Mantis religiosa, I think) we have many articles, but to look at the adults in their famous mating modes, have a look at our femme fatales of the Mantodea.