Some of the defenses of insects you see in the wild are amazing, while some are just pure gross. Some butterflies are poisonous to prevent being eaten, and some insects have venomous stings. One of the grossest defenses belongs to the bombardier beetle, which sprays a boiling chemical in a particularly unpleasant way. This video from National Geographic shows this beetle in action, and its gross defense. Read below to learn more about how this beetle defends itself in the nastiest way!
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About The Bombardier Beetle
The bombardier beetle, known scientifically as Brachinus, is a dark brown to black beetle with reddish-orange legs and head. The beetles are small in size, roughly half an inch to one inch in length. They are found on every continent except for Antarctica in habitats such as forests and grasslands, mostly staying near streams and under rocks. They are carnivorous insects that eat other insects such as caterpillars. Their most famous feature is their boiling chemical spray, which they shoot from their—believe it or not—butt.
The bombardier beetle mixes hydroquinone and hydrogen peroxide in its abdomen using specialized cells. When these chemicals combine, they trigger a strong reaction that generates heat and pressure, raising the temperature to around 200 degrees Fahrenheit. When the beetle is in danger—such as when it is eaten by a frog, as shown in the video above—it ejects the explosive spray from its anus with an audible pop. The chemicals cause burning and irritation, and if the beetle is already inside the stomach, it can cause internal damage. Because of this, the frog must vomit the beetle before any further internal damage occurs.
An example of a wound from a bombardier beetle’s chemical spray
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Effects of the Chemicals
The chemicals, while strong, do not normally kill the predators that have eaten the beetle. It simply acts as a way to force the predator to throw up. The chemical mixture has the potential to cause burns to the eyes, mouth, and stomach. So, while not completely lethal, the experience often makes predators more wary of eating these beetles. Bombardier beetles have relatively few predators because of their highly effective chemical defense, though some larger animals, such as toads, birds, and lizards, may occasionally attempt to eat them. As long as the beetle is not chewed or crushed, it can survive inside a predator’s stomach and is often vomited up alive—a phenomenon known as postingestion survival. Studies have shown that a significant proportion of bombardier beetles survive this process and remain active after being ejected.
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