Researchers at Tel Aviv University (TAU) examined the mechanical wear on digging valves located at the tip of the female locust’s abdomen, used to dig pits for laying eggs, and found that, unlike organs with remarkably high wear resistance such as the mandible (lower jaw), the valves wear down substantially due to the intensive digging.

“This is an instructive example of the ‘good enough’ principle in nature,” the researchers say. “Evolution saw no need to invest extra energy and resources in an organ with a specific purpose that performs its function adequately. We humans, who often invest excessive resources in engineered systems, can learn much from nature.”

The study was led by Dr. Bat-El Pinchasik from TAU’s School of Mechanical Engineering and Professor Amir Ayali from the School of Zoology at TAU’s George S. Wise Faculty of Life Sciences, Sagol School of Neuroscience, and Steinhardt Museum of Natural History. The article was published on November 25, 2024, in the journal Advanced Functional Materials.

“In my lab, we study mechanical mechanisms in nature, partly to draw inspiration for solving technological problems,” Dr. Pinchasik says. “Recently we collaborated with Professor Ayali, a locust expert, in a series of studies to understand the mechanism used by the female locust for digging a pit to lay her eggs.

“This unique mechanism consists of two pairs of shovel-like valves that open and close cyclically, digging into the soil while pressing the sand against the walls.”

“We know that many mechanisms in the bodies of insects in general, and locusts in particular, are exceptionally resistant to mechanical wear,” Professor Ayali adds. “For example, the locust’s mandibles, used daily for feeding, are made of a highly durable material.

“The digging valves, on the other hand, while subjected to substantial shear forces during digging, are used only three or four times during the female’s lifetime, when she lays eggs. In this study we sought to discover whether these digging valves, made of hard cuticular material, were also equipped by evolution with high resistance to mechanical wear.”

To address this question, the researchers examined the digging valves in three different groups of female locusts: young females that had not yet laid eggs, mature females kept in conditions that prevented them from laying eggs, and adult females that had already laid eggs three or four times. To analyze the internal structure and durability of the digging valves, the researchers used several advanced technologies: confocal microscopy, 3D fluorescent imaging, and a particle accelerator (synchrotron) in collaboration with a German team.

The findings indicated significant signs of wear in the valves and a lack of elements associated with high resistance to mechanical wear. Notably, no reinforcing metal ions, typical of extremely wear-resistant biological materials, were found in the valves.

“A female locust’s biological role is laying eggs three or four times in her life,” Dr. Pinchasik observes. “In this study, we found that evolution has designed her digging valves to meet their task precisely — no more and no less.

“This is a wonderful example of the ‘good enough’ principle in nature: No extra resources are invested in an organ when they’re not needed. As engineers who develop products, it is our duty to understand the precise need and design an accurate response, avoiding unnecessary overengineering.”