Nature is the best weapon engineer. Some living beings are equipped with a series of strategies and tools that it’s difficult to imagine they were generated by chance. In fact, devotees of creationism and intelligent design use these examples to vindicate their beliefs.
Let’s look at the case of the carabid beetles of the genus Brachinus sp. They seem harmless, but if they are known as bombardier beetles it is for a reason. They have a pair of chambers at the back end of their abdomen connected to the outside in which an incendiary chemical reaction takes place.
In one of them, the innermost one, a group of glands secretes hydroquinones and hydrogen peroxide. The other, connected to the outside, houses a mixture of two enzymes: catalase + peroxidase. When the beetle is endangered, the muscles around the inner chamber contract and expel the chemical mixture into the other chamber, where they come into contact with the enzymes. The peroxide is hydrolyzed, the hydroquinone is oxidized, and the resulting reaction reaches a temperature… of 100°C!
The enormous pressure generated by the resulting gases triggers two things: 1) it closes a valve to prevent the dangerous mixture from backing up into the internal chamber of the animal, and 2) it explosively ejects (sounds like a detonation) the burning, irritating spray resulting from the reaction in the direction of the danger. The gunner is not harmed thanks to its exoskeleton, but its victim will think twice before approaching this miniature bomb again.
However, its predators do not lag behind. Some rodents, knowing what will happen, quickly bury their prey to muffle the blast and then eat it.