This is How Bombardier Beetles Fire Explosives From Their Butts

The beetls have a special chamber in their abdomens where they mix together chemicals to produce an explosive reaction

bombardier beetle
Alex Wild/Visuals Unlimited/Corbis

Bombardier beetles are like the skunks of the insect kingdom — if skunks shot fiery acid at their enemies instead of just making them smell awful. And now, thanks to a new study, scientists know a bit more about how the bugs blast a chemical cocktail out of their rears without blowing themselves up.

Many species of beetles secrete chemicals to ward off predators, but it turns out that bombardier beetles have a special chamber in their abdomens where they mix together chemicals to produce an explosive reaction — complete with gun smoke, as you can see here:

Bombardier Beetle Blasts

The bombardier beetle then blasts its would-be predator with a chemical mixture that can reach up to 22 miles per hour at 100 degrees Celsius (212 degrees Fahrenheit​), writes Ed Yong for National Geographic:

“The beetle mixes its chemical weapons within glands in its abdomen, each of which consist of two chambers. The reservoir chamber contains a solution of hydrogen peroxide and hydroquinones—that’s the fuel, inert on its own but always on the cusp of extreme violence. The adjacent reaction chamber contains enzymes like peroxidise and catalase—that’s the match.”

When the bug is threatened, it touches the match to the fuel, which then forces its way out of an exit channel in it’s rear end. In order to figure out why the bombardier beetles don’t just explode, the scientists used ultrafast x-ray imaging to capture the moment the beetles pulled the trigger. They discovered that the beetle’s defense acts less like a missile launcher and more like a machine gun, firing between 368 and 735 pulses per second. Not only does this extend the range of the blast, but it might just save the bombardier’s life.

“A continuous spray would heat the beetle up a lot more,” potentially burning the bug, Christine Ortiz, one of the lead authors on the study, tells Yong. The split-second pauses in-between bursts allows the beetle to cool down. The mechanism works passively, meaning the bombardier beetle doesn’t even have to expend any energy to defend itself - just point and squeeze.

"Understanding how these beetles produce – and survive – repetitive explosions could provide new design principles for technologies such as blast mitigation and propulsion," said Ortiz and Eric Arndt, another lead author, in a press release.

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