An alien-like creature with a lightning-fast gripping tool: How the mysterious trap mask of the dragonfly larvae works has now been clarified for the first time. They were also able to illustrate the special biomechanical concept that enables the rapid movement using a robot system. The dragonfly larvae robot also shows the potential of the natural patent for the development of fast and precise movement processes in technology, the scientists report.
They whiz elegantly through the air on the banks of ponds and lakes – but at this winged adult stage the dragonflies only spend a comparatively short period of their lives. Most of the time they exist as larvae at the bottom of the water. There the rabid robbers lurk mosquito larvae and other prey. Fate suddenly overtakes their victims: dragonfly larvae have a special trap mask on their heads that they can snap forward in a split second to grab prey (see video).
But how does the bizarre gripping instrument work? So far, there have only been assumptions about the biomechanical principle that enables high-speed movement. It was assumed that it would have to be mainly hydraulic propulsion. But a team of researchers from Christian Albrechts University in Kiel wanted to know more about it. To decipher how it works, they examined the insect larvae ‘s trap mask with the help of various interdisciplinary analysis techniques. Modern computer tomography methods in particular provided insights into the internal structure of the tiny structure.
A dual catapult system
So it turned out that there is no hydraulic system. Instead, the propulsion of the mouthparts of the dragonfly larvae works via a controllable catapult system: an inner, elastic structure in the dragonfly’s head that is tensioned by a muscle like a spring. The energy of the muscle is stored and suddenly released, similar to a tense bow. Such systems are widespread in the animal kingdom – for example with locusts, cicadas and mantis shrimp. But there is one special feature of dragonfly larvae that has not yet been described: there is a synchronized, dual catapult system. “Two catapults are in one structure, but can be pre-tensioned individually. They work together to precisely control the trap mask, ”explains co-author Alexander Köhnsen.
In order to confirm and illustrate this functionality, the researchers initially visualized the complex processes using 3D animations. They then used a 3D printing process to produce a robot that simulates the gripping mask of the dragonfly larvae. “One of the great advantages of bio-inspired robots is the ability to test ideas about biological operating principles that would be very difficult to test otherwise. Robotics ideally works in two directions: We learn something about biology and develop something technically applicable, ”says first author Sebastian Büsse.
Potential for robotics
The simulations and above all the dragonfly larvae robot made it clear that the independent control of two catapults within one system can enable better control of fast movements. This is an interesting concept for applications in robotics, say the researchers. “The system allows better control of a catapult-driven process, for example jumping, which means that additional control and stabilization systems could be smaller and lighter. This could increase the performance and efficiency of such robots, ”says Büsse.
Senior author Stanislav Gorb concludes about the study: “After a variety of modern structure and movement analyzes, ultimately developing a functioning, bio-inspired robot that, thanks to its special structure, enabled a deeper insight into the functioning of the biological model – that was fantastic.”
Source: Christian-Albrechts-Universität zu Kiel, specialist article: Science Robotics, doi: 10.1126 / scirobotics.abc8170
A dragonfly larva attacks prey with its catching device. (Video: Christian-Albrechts-Universität zu Kiel)