Creation/Evolution Journal

The Bombardier Beetle Myth Exploded

Dr. Duane T. Gish, assistant director of the Institute for Creation Research (ICR) has made some extravagant and unfounded claims about the bombardier beetle (genus Brachinus). This beetle defends itself by shooting boiling-hot fluids out its rear end at its attackers; Gish argues that no ordinary beetle could have slowly evolved into a bombardier beetle through any conceivable transitional forms because a transitional beetle with an incomplete mechanism would have either been burdened with a load of useless baggage, or else have blown itself to smithereens. In this article, we shall see how badly Gish has distorted the facts about this insect.

In his book Dinosaurs: Those Terrible Lizards (Creation-Life Publishers: San Diego, CA, 1977), Gish lays out his entire argument that transitional beetles are inconceivable. He describes how the bombardier beetle's explosive defense system is supposed to work, claiming to derive his information from the German entomologist Dr. Hermann Schildknecht. His argument is based on this description of the beetle's mechanism, and stands or falls with it:

This scientist [Dr. Hermann Schildknecht] found out, first of all, that the bombardier beetle mixes up two kinds of chemicals—hydrogen peroxide and hydroquinone. Now the marvelous thing about this is, if you or I went into a chemistry laboratory and mixed up these two chemicals — BOOM! We would blow ourselves up.

But not the bombardier beetle. He's too smart. When he mixes up these two chemicals he makes sure he adds another kind of chemical, called an inhibitor. The inhibitor somehow prevents the other two chemicals from blowing up. In other words, they just sit there together real peaceful like. The beetle then stores this liquid in two storage chambers, ready to be used when needed. . . .

How does Mr. B. B. make the chemical solution explode just at the right time, in spite of the fact that it contains an inhibitor? Dr. Schildknecht found out just at the exact moment Mr. B. B. wants to fire his two cannons, he squirts in an anti-inhibitor. The antiinhibitor neutralizes (knocks out) the inhibitor, and the two chemicals (the hydrogen peroxide and the hydroquinone) can then react violently together and explode. (pp. 51-52)

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Thus Gish is maintaining that the bombardier beetle juggles four chemicals in its defense mechanism. The hydrogen peroxide and hydroquinone spontaneously explode unless an inhibitor is added to prevent the explosion. The beetle fires off its defense mechanism by adding an anti-inhibitor to this mixture. Gish bases his entire argument on this inhibitor model. If any of the four chemicals, any of the organs, or the nervous system mechanism were missing in any of the transitional forms, then either the beetle would blow itself up, or else it would be lugging around a lot of useless baggage. Obviously, natural selection would not select for either one. At any rate, that's how Gish argues.

Actually, Dr. Gish totally misrepresents Dr. Schildknecht, who says absolutely nothing about an inhibitor. On the contrary, hydrogen peroxide and hydroquinone do not spontaneously blow up when mixed together; they just slowly turn brown as they oxidize. The only time they explode is when the beetle forces them to by adding two catalysts, a catalase to decompose the hydrogen peroxide, and a peroxidase to oxidize the hydroquinones and thereby break them down into the simpler quinones. Apparently Gish's translator does not read German very well. Drs. William Thwaites and Frank Awbrey of San Diego State University in California have even shown Gish there is no inhibitor and that the two explosive chemicals do not explode spontaneously. Yet despite this, Dr. Gish still continues to use this false argument.

Thwaites and Awbrey teach a two-model Evolution vs. Creation course at San Diego State. Leading creationists such as Dr. Gish present the creationist viewpoint during one session, and then Awbrey and Thwaites present the findings of empirical science during the following meeting. At one such rebuttal session in the spring of 1978, Thwaites gingerly mixed hydrogen peroxide and hydroquinone solutions together. The two professors took elaborate precautions to protect the class in case Dr. Gish's biochemistry turned out to be correct. The solutions only turned brown, failing to explode.

This is an easy experiment to duplicate. You- can even try it at home, since hydroquinone can be purchased from your local photography shop (it's used for photographic developer), and hydrogen peroxide is available at your supermarket or drug store (it's used in women's hair coloring). This allows you to prove to your own satisfaction that hydrogen peroxide and hydroquinone do not spontaneously explode.

When Thwaites and Awbrey confronted Gish with this fact, he became flustered, and said that somehow the German word for "unstable" had been mistranslated as "explosive."

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When they asked him what his source was, he replied that he had gotten his information from Hermann Schildknecht, Eleonore Maschwitz. and U. Maschwitz. "Die Explosionschemie der Bombardierkafer (Coleoptera, Carabidae)," Zeitschrift fur Naturforschung, Vol. 23 (1968), pp. 1213-1218. The purpose of this article is to study the nature of the catalysts that make the otherwise inert hydrogen peroxide and hydroquinone explode:

During the "pop," the contents of the paired pygidial defense bladders of the bombardier beetle (hydrogen peroxide and hydroquinone) are squeezed in small portions into chitinous chambers, and there they are explosively transformed into oxygen, quinone, and water. This explosion-chamber reaction is catalyzed by enzymes, which are emptied as a dark brown 40-60% albumin solution out of one-celled annex-glands into the front chamber. [My own translation]

Thus Schildknecht is saying that the hydrogen peroxide and hydroquinone do not explode until the enzymes make them do so, and mentions nothing about any inhibitor. Let us see in more detail what Schildknecht has to say on the beetle's explosion mechanism.

Schildknecht's diagram of the insect's defense organs shows that there are two chambers, the larger inner chamber (called the "reservoir" by Eisner and the "collection bladder" by Schildknecht) empties into the smaller outer one (called the "vestibule" by Eisner and the "explosion chamber" by Schildknecht), which in turn empties into the outside world through an opening near the anus. There are two sets of these organs, one on either side of the anus. The collection bladder collects hydrogen peroxide and hydroquinone, which just sit there without exploding. The explosion chamber collects a brown gooey mixture of enzymes. This chamber has a thick chitin wall with numerous little holes in it through which single-celled glands secrete and deposit the enzymes into the chamber. When the insect becomes excited, a muscle opens up a little door on a hinge. Through this opening the two chemicals are forced into the explosion chamber, where the enzymes make them explode out of the insect's derriere as oxygen, quinone, and water. (The door opens into the explosion chamber so that the explosion will force the door shut and not injure the collection bladder. Schildknecht explains the chemistry of this reaction clearly:

Not only did the results of our earlier work on the defense system of the bombardier beetle give the surprising result that this beetle manufactures a 25% solution of hydrogen peroxide and a 10% solution of hydroquinone, but we can now also show that the enzyme that sparks off these chemicals is also stored in an extraordinarily high concentration. In the explosion chamber a 40-60% albumin solution is stored which consists of one third peroxidase and two thirds catalase. We are concerned here with the secretion of the annex-glands which empty into the front chamber of the pygidial bladder, an extension of the anus.

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Gish was made aware of all this in the spring of 1978. Even though he continued to insist that this insect could not have evolved and that it has some kind of inhibitor to keep the two chemicals from oxidizing, he reluctantly admitted that hydrogen peroxide and hydroquinone do not spontaneously explode when mixed, and that Schildknecht has nothing to say about any inhibitor.

Nevertheless, Gish still continues to use his old description in his debates. For instance, on January 17, 1980, in a debate with Dr. John W. Patterson at Graceland College, Lamoni, Iowa, Gish said:

The bombardier beetle is a remarkable little creature that has this explosive mechanism. He stores two chemicals in a storage chamber, and he puts in an inhibitor to keep it from exploding or decomposing. He squirts it in the combustion tube, and then he adds an antiinhibitor, and there all the enzymes there [sic]—and boom! An explosion goes off right in the face of his enemy. Beautifully timed! Beautiful mechanism! You have to have thick storage chambers, you have to have the two chemicals, you have to have an inhibitor, you have to have an anti-inhibitor, you've got to have those combustion tubes, you have to have the communication network all present and functioning, just as you have to have every part on the rockets to go to the moon present and functioning. How are you going to explain that step-by-step by evolution by natural selection? It cannot be done!

Gish already knew better. Why would he repeat an old error? If he is this unreliable in areas where we can check up on him, then how can we trust him in areas where we cannot? But even if his facts were beyond reproach, we would still have difficulty taking him seriously because he brings up the bombardier beetle to help prove that fire-breathing dragons may have actually existed. In the very book in which he describes the bombardier beetle (Dinosaurs: Those Terrible Lizards), he argues that old legends, Job 41:18-21, and the bombardier beetle all suggest that the unique crests on the heads of some duck-billed dinosaurs were the chemical storage tanks for their flame-throwing mechanisms. These dinosaurs were thus the fire-breathing dragons of myth and legend! Need I say more?

Although the main purpose of this article is to show that Gish's description cannot be trusted, we should take a little time to see how the bombardier beetle's defense mechanism could have gradually evolved. There's no problem explaining where the hydroquinone and the hydrogen peroxide came from.

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As Thomas Eisner shows in his article "Chemical Defense Against Predation in Arthropods" (Chemical Ecology, 1970, pp. 157-215), hydrogen peroxide is a normal metabolic byproduct in insects, and various quinones are used to harden (or "sclerotinize") the cuticle of insects. All kinds of insects therefore secrete these chemicals. As a byproduct, hydroquinone tastes bad to predators and is the chemical that makes stink bugs stink. So, if an insect's cuticle became indented, forming little sacs to store some of this hydroquinone, it would have an advantage over its fellows even if its storage mechanism was not yet very efficient.

Schildknecht himself points out that the carabid family of beetles has little sacs like this. They have glands that exude enzymes into pygidial bladders that empty into the anus, even though these don't explode. So, even though the bombardier beetle is the only carabid beetle to shoot boiling liquid at its enemies, the other carabid beetles, living in different ecological niches, survive very well because, with their thick-walled little sacs, they can poison their enemies but not themselves.

Therefore, all the pre-bombardier beetle had to do was direct some of that hydrogen peroxide into its collection bladder, develop a little valve between the collection bladder and vestibule chamber, and finally supply the catalase and peroxidase in the vestibule. The hydrogen peroxide would make the insect more poisonous to eat than it was before. A muscle that pulled the duct between the two chambers open, and relaxed to let it close, would help the beetle be more selective about its poison discharges. Even if this valve structure was crude at first, it would have survival value until the side of the duct attached to the muscle could evolve into a little door. The enzymes would be useful the moment they appeared. Even if the beetle's new firing mechanism could not be aimed all that well or if the chemicals were not being secreted in the best proportions at first, the mechanism would still be useful from the start, and the beetle could refine it in time.

So, when Gish says, "How are you going to explain that step-by-step by evolution by natural selection? It cannot be done!" he is merely admitting that he has little ability in problem solving.

By Christopher Gregory Weber
This version might differ slightly from the print publication.