Tom Weihmann

Cockroaches have always seemed larger than life, but a new study really puts this outsized effect in perspective.

Conducted by researchers at the University of Cambridge, the study directs readers to take a closer look at cockroaches, specifically their mouths. This may seem an unwelcome gesture, but the results—which are surprisingly digestible—offer a new perspective on insects overall, one that could aid both evolutionary understanding and the future of engineering.

Published in the journal in PLOS ONE, the study found that cockroaches can generate a bite force 50 times stronger than their own body weight—a tactic they use for chewing on especially tough materials like wood. In order to accomplish this, researchers determined they use a combination of "fast and slow twitch muscle fibers" to give their mandibles a "force boost."

This means that, in relative terms, cockroaches can bite with a force about five times stronger than the force that humans can with their own jaws.

Tom Weihmann from the University of Cambridge's Department of Zoology and lead author of the study, told Fusion that cockroaches "apply relatively weak but quick bites when speed is crucial but employ slower, stronger muscle fibers when maximum bite forces are required."

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Weihmann said that while numerous studies have been published regarding biting mechanisms in vertebrates such as mammals, lizards, and dinosaurs, the bite physiology of insects, "a group which is equally important to vertebrates in ecological terms," has not been thoroughly explored. He said they chose to study cockroach bites in large part because they are "extraordinarily ordinary insects" when it comes to their biting abilities.

A micro-computed tomography image of a cockroach head showing the driving muscles of the left mandible.
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Larger animals like vertebrates have jaws full of teeth that are used for everything from grinding food to threatening away other animals. Insects such as cockroaches have entirely different "biting mouthparts" made up of a pair of horizontally aligned blade-like jaws, or mandibles. These mandibles are used for shredding food, digging, transportation, defense, and even feeding offspring.

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Arthropods, including insects, also have exoskeletons with muscles enclosed in rigid shells. According to the study, this limits "muscle thickening." In insects this can cause the jaw muscles to extend into the head capsule and compete for space with other essential organs, like the central nervous or even the digestive system.

In conducting the experiment, Weihmann and his team measured the force of 300 cockroach bites. They found that while the weaker bites are generated by relatively fast muscle fibers, the stronger bites are generated by additional muscle fibers that take time to reach their maximum force.

"The employment of slow muscle fibers allows very efficiently generated muscle forces with only a minimum of cross section area, and therefore head volume, required," said Weihmann.

So why does this matter?

According to Weihmann, there are several reasons why revealing the internal mechanisms of a cockroach bite may prove insightful:

  • It may help researchers better understand pest species, and therefore better exterminate them.
  • It may allow new insights into the evolutionary development that led from omnivorous ancestors to specialized carnivores.
  • It could help "engineers to further miniaturize their apparatuses" in the form of "bioinspired engineering."

"Insects are small and their body is highly adapted to being small," said Weihmann. "A current technological development is the increasing miniaturization of many mechanical implementations. Such devices face the same limits and constraints as insects did for hundreds of millions of years."

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Micro probes inserted into blood vessels or micro surgical instruments are examples of technological innovations in this vein.

Cockroaches are also "good runners and climbers," according to Weihmann, who said examining these behaviors may help design robots with increased running and climbing abilities. He's already conducted a cockroach climbing study that he plans to publish next year.

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Maybe cockroaches will evolve to be smaller and smaller until one day they cease to exist. In the meantime, it helps to remember that if the billions of cockroaches in the world suddenly disappeared, it would be very harmful for "forest health and therefore indirectly on all the species that live there," according to Srini Kambhampati, professor and chair of the biology department at the University of Texas at Tyler. This is because cockroaches feed on decaying matter and release valuable nitrogen into the soil, which plants rely on.

If only they would just stay outside.