Engineers could learn a thing or two by observing the dynamical brilliance of insects.

Mantis Momentum

It’s a safe bet that when Strauss wrote the Blue Danube waltz, he wasn’t picturing a praying mantis leaping like a ballerina. But the tune fits. Watch the video of a mantis jump, via New Scientist — it will make you chuckle! Behold the elegant move a juvenile mantis makes while jumping in slo-mo to a rod placed by researchers. They wanted to learn how the bugs jump so unerringly to a target. These bugs know the Law of Conservation of Angular Momentum! — and, mind you, they’re babies.

Work at the University of Cambridge shows how they do it.

During the jumps, the insects rotated their legs and abdomen simultaneously yet in varying directions — shifting clockwise and anti-clockwise rotations between these body parts in mid-air — to control the angular momentum, or ‘spin’. This allowed them to shift their body in the air to align themselves precisely with the target on which they chose to land.

And the mantises did all of this at phenomenal speed. An entire jump, from take-off to landing, lasted around 80 milliseconds — literally faster than the blink of a human eye. [Emphasis added.]

That’s also a lot faster than a cat landing on its feet. The dry details of the physics are contained in a paper in Current Biology, but the authors must have had fun watching the playback from their high-speed cameras. The paper’s title is revealing: "Mantises Exchange Angular Momentum between Three Rotating Body Parts to Jump Precisely to Targets."

The researchers figured that the bugs don’t just get it right on take-off. They can manipulate their bodies in mid-air — within that 80-millisecond journey — to adjust for a precision landing. When they prevented the abdomen from flexing, the mantises were unable to control themselves. They made it to the rod, but bumped their heads:

We show that when making targeted jumps, juvenile wingless mantises first rotated their abdomen about the thorax to adjust the center of mass and thus regulate spin at takeoff. Once airborne, they then smoothly and sequentially transferred angular momentum in four stages between the jointed abdomen, the two raptorial front legs, and the two propulsive hind legs to produce a controlled jump with a precise landing. Experimentally impairing abdominal movements reduced the overall rotation so that the mantis either failed to grasp the target or crashed into it head first.

The team compared this skill to aphids, anole lizards, ants, and cats. "Flightless animals have evolved diverse mechanisms to control their movements in air, whether falling with gravity or propelling against it." That’s falling with style. Remember the interacting gears of the planthopper? Cats and geckos use their tails for balance, while insects adjust their legs.

Convergent evolution works many miracles, apparently. Some scientists, though, see some of the design implications. Over at The Conversation, Burrows and Sutton envision entrepreneurship in the study of insect aerobatics. "Outside the insect lab, learning from the way mantises solve the problem of stability may aid the design of small jumping robots, where controlling spin continues to be a challenging problem," they say.

Mosquito Surface Tension

Mosquitoes have a knack for landing on water without getting wet. That caught the eye of Chinese physicists, says a reporter for Science Magazine. "Mosquitoes may not seem divine, but they can walk on water, thanks to their ultraflexible legs," Emily Conover writes. Take a look at the photo in the article showing an extreme close-up of the tiny bug, poised on the surface, as if walking on rubber. Most objects of equivalent mass would sink. Naturally, the physicists got their instruments out to measure the forces involved. Insect legs have three parts: the femur, tibia, and tarsus. The tarsus turns out to be the most important.

The secret of the tarsus is its flexibility, they found — stiff tarsi exert less force before breaking through the water’s surface. A flexible tarsus, in contrast, can support up to 20 times the weight of a mosquito by conforming to the water’s surface, the researchers report online today in AIP Advances. Mosquitoes can adjust the level of support by changing the angle at which tarsi impact the water, allowing them to walk, take off, and land in gusty weather.

Once again, this design work motivates entrepreneurship. "Understanding the science of mosquito legs could be useful for the development of miniature water-striding robots, researchers say," hopefully less annoying than the living kind.

An item from the American Institute of Physics publication AIP Advances calls this a "unique adaptation" in mosquitos and water striders. They still don’t have it figured out completely.

That’s two more humble creatures that astonish scientists with their command of physics. Design is no science stopper. The sequence is clear in these and many other cases: See design — think design — study design. That’s what leads to understanding. Understanding then leads to inspiration; and inspiration leads to application.