How hard can insects bite? Having a strong chewing device makes it easier to crush harder food and to succeed in battles with enemies. Biologists from the University of Bonn now present a mobile system (forceX) for measuring the bite forces of small animals, along with the forceR software to evaluate the data. This makes it possible to understand how bite forces, for example from insects, have evolved. The final version is now published in the magazine Methods in Ecology and Evolution†
The praying mantis wobbles a little in the scientist’s hand. When the insect approaches the sensor, it defends itself by biting the two metal plates that transfer the pressure to a piezo crystal. The crystal generates a load-dependent voltage that is sent to a laptop through an amplifier. Curves appear on the screen, some of which rise steeply and reach a vibrating plateau before falling back to zero. Sometimes the ascent and descent are flatter depending on how fast the particular insect approaches maximum force when biting.
Hardly any data on bite force
“Hardly any data is available on how hard insects can bite,” said Peter T. Rühr, a PhD student at the Institute of Evolutionary Biology and Ecology at the University of Bonn. With their sensor system, forceX, the researchers aim to explore how insects’ mandibles, musculature and head shape have evolved to meet the challenges of their respective environments. “It may not always be beneficial to be able to bite hard, because the ability to bite strongly requires higher energy costs,” says Rühr. For example, the bite force may depend on what food an insect is feeding or whether it needs the lower jaws to defend itself.
The team led by prof.dr. Alexander Blanke, who has received a Starting Grant from the European Research Council (ERC), has further developed existing systems for measuring bite forces.
In the measurement set-up of the researchers at the University of Bonn, a stereomicroscope, similar to a strong magnifying glass, is used to detect whether the lower jaws of the insect under study come into contact with the metal plates of the sensor in the right place. The lower plate is immobile, while the upper one transmits the power to the sensor via a rocker.
Flexible adjustment to lower jaw size possible
“Depending on the size and opening angle of the lower jaws, we use interchangeable bite plates of different sizes,” explains Rühr about the progress. “This allows the sensor to be adapted to the specific requirements of the animals over a relatively large range.” The complete system is battery powered and can therefore be used for mobile measurements, even in the wild.
The researchers use a plastic container for stinging insects. The animals disappear completely into the bottle, with only the head with its mouthparts sticking out of a small hole in the front. Rühr: “This allows us to better position the insects without having to hold them in our hands.”
Usually the animals do not need much persuasion before they bite. They feel uncomfortable in the unfamiliar environment and fight back with defensive bites. If this instinctive behavior fails to materialize, the researchers stroke the insects’ heads with a delicate brush – at the latest, the insects will close their jaws.
High accuracy of measurement
For publication in Methods in Ecology and Evolution, the researchers determined the accuracy of the system: they did this by attaching different weights, ranging from one gram to almost one kilogram, to the movable metal plate. A total of 1,600 repetitions show that the deviation between measurements is a maximum of 2.2 percent. “That’s very accurate,” says Rühr. The system can also be used to measure, for example, the strength of scorpions or crab claws.
Rühr and Blanke built the system during their time at the University of Cologne, partly with the local precision engineering workshop. At the University of Bonn, they further optimized it and performed the accuracy measurements. The manuscript also describes the new “forceR” software, which allows the evaluation and comparison of bite force values and shapes of the bite curves. The researchers do not want to market the bite force sensor system. “On the contrary, the results presented in Methods in Ecology and Evolution form the basis for replicas,” says Rühr. Essential parts of the sensor can even be reproduced with a 3D printer.
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Peter T. Rühr et al, forceX and forceR: a mobile setup and r package for measuring and analyzing a wide range of animal clamping forces, Methods in Ecology and Evolution (2022). DOI: 10.1111/2041-210X.13909
Provided by Rheinische Friedrich-Wilhelms-Universität Bonn
Quote: Measuring insect bite force (2022, June 23) retrieved June 23, 2022 from https://phys.org/news/2022-06-insects.html
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