MIT, Cambridge – It may be just a small insect, but the Bombardier Beetle releases a nasty-smelling liquid with gun smoke whenever it senses dangers.

Doctoral students at MIT carried out a research that has revealed the mystery behind this creature’s highly active machine-gun bum.


Eric Arndt and Christine Ortiz from the Department of Materials Science and Engineering at Massachusetts Institute of Technology (MIT) initiated this research with Wendy Moore from University of Arizona.

“Previous researchers suggested that the pulses were caused by muscle contractions or by a fluttering of the exit duct during the explosions,” said Wendy Moore.

500 beetles analyzed

For the research, the internal working of spray pulsation was observed in live Brachinus Elongatulus beetles found in southern Arizona. Out of the 500 insects that were examined, 30 discharges were recorded by 14 insects. This was captured in a high-speed video that showed the researchers what all was happening inside the reaction chamber of the beetle.

Analyzing the beetle through photographs from an ultra-fast camera technique, they found that this was an extremely effective defense mechanism. Not many predators had the means to fight off this defense and thus the beetle protects himself.

Mixing of chemicals in defense chamber behind the explosions

The researchers found that the Bombardier beetle was capable was able to synthesize the foul-smelling chemical through mixing of two chemicals in its hindquarter protective chamber. When the insect was dissected, the two glands were the chemicals that cause the action, are stored were found and there was a special explosive chamber with layers.

‘It turns out the expansion membrane of the reaction chamber acts as a passive closure mechanism, which is something that had not been described or even predicted before this study. We also discovered that the chamber’s anatomy varies between female and male beetles,” said Moore.

The researchers have concluded that by these multiple explosions, a large volume of protective spray was released that was aimed at the target with great speed and force.

“This is truly one of the most remarkable and elegant defensive mechanisms documented to date,” the researchers added.

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