The Bombardier Beetle – A Bug That Can Create a Chemical Bomb?

 In Animals

IN HIS EPIC encyclopedia Natural History, the great Roman naturalist Pliny the Elder wrote of the bonnacon, a sort of bull whose defensive strategy was to hit its foes with blasts of dung “so strong and hot, that it burneth them that follow after him in chase, like fire, if haply they touch it.” Natural history in Pliny’s time, you see, consisted of a good amount of hearsay. From 12-year-old boys, apparently.

There is, though, a remarkable real-life version of the bonnacon: the bombardier beetle. While it doesn’t weaponize its dung per se, it has evolved a cannon in its caboose, where chemicals mixed in a special chamber violently burst out of the critter in a boiling, noxious, pungent spray that can repel even the most daring of predators.

There are hundreds of species of bombardier beetles all over the world, with various defensive mechanisms. Some have non-explosive, foamy excretions of chemicals, while others like the African bombardier beetle can actually aim their explosive spray in virtually any direction like an angry lawn sprinkler. We’ll be talking about the latter here. The spraying bombardier beetles, not lawn sprinklers.

In the bombardier’s abdomen is a chamber that holds a mixture of hydrogen peroxide–the stuff you put on cuts and no, you shouldn’t try disinfecting your wounds with bombardier beetle explosions–and chemicals called hydroquinones. When the beetle feels threatened, this chamber empties into another reaction chamber that contains catalysts to kick off the explosion.

Here the hydrogen peroxide rapidly decomposes into oxygen and boiling water, while the hydroquinones oxidize into benzoquinones–highly irritating chemicals that have been known to stain the skin of human handlers a yellowish brown for up to three weeks. This mix explodes out of the beetle, not as a single stream, but as a volley of rapid-fire blasts, in what scientists have likened to the pulsing propulsion system of Germany’s V-1 “buzz bomb” in WWII. The consequent chemical burn (free idea for a metal band name: The Consequent Chemical Burn) incapacitates smaller attackers like ants, and spooks out much, much larger foes as well, such as unfortunate amphibians.

“You’ve got 100 degrees centigrade temperature, you’ve got a chemical burn, the steam comes off like a smoke, and then also the reaction kind of hisses,” said entomologist Terry Erwin of the Smithsonian Institute. That adds up to a bad situation for any hungry frog that pokes its tongue in the wrong place. “There might be 200 of these beetles under one rock, and they all fire at the same time, and you’ve got a smokescreen, or vaporscreen, as it were,” Erwin said.

An incredible defense to have evolved, for sure, but the chemicals here are actually quite uncomplicated. Hydrogen peroxide is a natural byproduct of metabolism in almost all living creatures. And insects use quinones to harden their shells. The bombardiers have just figured out how to store these chemicals instead of breaking them down or using them up.

The bombardier can fire these compounds more than 20 consecutive times before running out of ammo. But how can the beetle flash-boil chemicals to over 200 degrees Fahrenheit inside itself without melting? I mean, I’ve been on this planet for 29 years and I can’t even boil water in a pot without somehow injuring myself.

“The insect cuticle is pretty tough stuff, and this reaction chamber where it all happens is very, very dense-walled,” said Erwin. “And when they open the turret, then all of this stuff goes directly out of the beetle.”

“They can actually swing that turret around and shoot over their head, shoot to the right, shoot to the left, underneath them,” added Erwin. “The only place they can actually not shoot is where their mouthparts are.” You wouldn’t want to get a taste of your own medicine if you were one of these beetles, now would you?

According to a study by the legendary late ecological chemist Thomas Eisner, such an incredibly evolved trait was likely driven by one of the world’s feistiest selection pressures: ants. You see, to escape swarming ants, ground beetles like the bombardiers have to unfurl their wings from covers and are unable to take flight as rapidly as, say, a bee. Having such a dexterous turret allows the bombardier to hold its ground against the ants to buy time, deftly dispatching the attackers clambering over its body. Indeed, some bombardier species’ bum cannons are so effective that their wings have even become vestigial and useless.

Creation or Random Chance?

Random evolutionary theory has big problems when attempting to explain the existence and complexity of the bombardier beetle by means of random, chance happenings. Each stage in the evolution of its special chemicals would have led to its destruction. This one-half inch insect mixes chemicals that violently react to produce something similar to an explosion. How could the bombardier beetle have evolved such a complex means of defense without killing itself in the process? This problem has the members of the evolutionary establishment scratching their heads. Evolutionary theory says that you lose it if you don’t use it. But, how do you use it unless you have it in completed and in fully functional form?

We have two options then. One is to believe that a mindless, random, chance process brought into existence exactly what would be essential for the creature to maintain life and defend itself. The other option is that an intelligence designed and created precisely what was needed for the welfare of the creature and encoded the information in its genes. With random evolution, a new enzyme or chemical or organ or fin or beak or bone will have to randomly, mindlessly, unexplainably evolve until the creature gains its new improvement.

The bombardier beetle is irreducibly complex. Remember back in fourth grade when we reduced fractions down until they could be reduced no farther? This beetle cannot be reduced! If it doesn’t have all its parts, it can’t defend itself or, even worse, it could blow itself up. Naturally, it could not evolve after it blew itself up and was dead, so how did it get here?

To prevent its own destruction, the little bug manufactures a chemical, called an inhibitor, and mixes it in with the reactive chemicals. But with the inhibitor, it would not be able to use the expulsion of hot, burning liquid and gases to discourage its enemies. A spider would eat it because the beetle has no solution to exploit to protect itself. Again, we have a dead beetle. Dead bugs cannot evolve the next chemical needed to release the protective reaction. That chemical turns out to be an anti-inhibitor. When the anti-inhibitor is added to the other chemicals, an explosive reaction does occur and the beetle is able to defend itself.

There is still another problem, however. The beetle must have an especially tough “combustion chamber.” That chamber must have an outlet for the violent reaction to release its energy or once again, we have a dead bug. Problem solved: this unique creature has the necessary equipment, including twin-tail tubes to “exhaust” its defensive reaction. These tubes can be aimed at enemies in a 180° arc from straight to the rear, to directly toward the front. Amazingly, it does not shoot friendly creatures but only its enemies! How does a one-half inch long insect know how to aim at and shoot potential enemies?

When the little bug shoots its cannons (and it can shoot either side individually or both sides together) all we hear with our human ears is a “pop.” But it is not just a single pop. It is a series of sequential pops that sequence so fast we only hear one “pop.” If it was just one big POP, it would be like lighting the after-burners on a jet engine and the diminutive creature would blow itself out of the picture. But with a sequential pop it can hang on with its little legs and remain in place! Incredible!

How did its incredibly complex nervous system and advanced chemical system evolve? There is nothing exactly like bombardier beetles in the entire animal kingdom. Is this an example of the “impersonal, plus time, plus chance” or is it an example of a special, intricate creation?

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