Insect Chemical Warfare

An amazing species of beetle, tired of lizards and birds talking smack, developed a powerful cocktail of pain that fires from its rear

Bombardier beetles are ground beetles (Carabidae) in the tribes Brachinini, Paussini, Ozaenini, or Metriini - more than 500 species altogether. The most popular and widespread is genus Brachinini.

The Bombardier beetle earns its name from its unbelievable ability to fire a boiling hot, poisonous chemical concoction at its attackers. The burning liquid is the result of a chemical reaction that reaches temperatures exceeding 212 degrees Fahrenheit and explodes outward at anything that dares to cross its path.

Bombardier Beetles range in size from 2.0 mm overall length (Mastax) to 30 mm in length (Aptinomorphus) and can be found all over the world, from the United States and Mexico to Australia. They live under rocks or pebbles in cool, sandy soil, usually near a stream or a lake. Aggregating in groups during the daytime, they are usually active at night. There exist several different types of Bombardier Beetles, which employ slightly different types of defensive structures and chemistry but generally the same method of defense—shooting at predators when threatened and then running away.

Bombardier beetles store two separate chemicals (hydroquinone and hydrogen peroxide) that are NOT mixed until threatened. When this occurs the two chemicals are squirted through 2 tubes, where they are mixed along with small amounts of catalytic enzymes. When these chemicals mix they undergo a violent “exothermic” chemical reaction. The boiling, foul smelling liquid partially becomes a gas and is expelled with a loud popping sound. A more detailed description of the process follows:

Secretory cells produce hydroquinones and hydrogen peroxide (and perhaps other chemicals, depending on the species), which collect in a reservoir. The reservoir opens through a muscle-controlled valve onto a thick-walled reaction chamber. This chamber is lined with cells that secrete catalases and peroxidases. When the contents of the reservoir are forced into the reaction chamber, the catalyses and peroxidases rapidly break down the hydrogen peroxide and catalyze the oxidation of the hydroquinones into p-quinones.

These reactions release free oxygen and generate enough heat to bring the mixture to the boiling point and vaporize about a fifth of it. Under pressure of the released gasses, the valve is forced closed, and the chemicals are expelled explosively through openings at the tip of the abdomen. Each time it does this it shoots about 70 times very rapidly. The damage caused is fatal to attacking insects and small creatures and is painful to human skin.

Bombardier beetles have come to public attention in recent years largely because of arguments put forward by creationists; particularly in the children’s book Bomby the Bombardier Beetle. A large debate has raged on regarding how the Bombardier proves or disproves evolution.

On one side of the argument, creationists state that because various components needed to make the system work appear to provide no benefit in themselves, meaning the entire system would have to be created at once. This, they say, indicates that it is the product of intelligent design. Without all of the necessary elements in place, and a means for control, the beetle would blow itself up.

On the other side, it is believed that the system could have very well formed over time. In one demonstration, biologist Richard Dawkins mixed together hydroquinone and hydrogen peroxide in an artificial environment. No reaction occurred - a catalyst was required. Dawkins’ point was that as the beetle’s defensive mechanism evolved, the intermediate stages would not explode - the chemicals would not react without a catalyst, and the concentrations of catalyst in its body could increase with evolution over time.

Regardless of all of the debate and speculation, one thing is for sure; the Bombardier Beetle is a pretty amazing creature that I would not want to mess with. I wonder, if you were walking along in the forest and you stepped on one; would it inadvertently mix the chemicals and trigger a small explosion?

Further Reading:
- Learn more about Bombardier Beetles at Wikipedia.org
- Read Bombardier Beetles and the Argument of Design
- The Bombardier Beetle at BugGuide

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Previous Comments

1. I can do that.

   Posted by pants  on  04/05/06  at  06:49 PM

2. fap fap fap

   Posted by O Rly  on  04/05/06  at  10:12 AM

3. fark fark fark

   Posted by bill  on  04/04/06  at  11:24 PM

4. I wonder if they can be trained.  Think of the possibilities.  You could keep a bunch of them as pets instead of that attack pit bull you’ve always wanted.  Hmm....

   Posted by superfreeq  on  04/04/06  at  08:28 PM

5. I never knew there was such a thing, nice

   Posted by troy  on  04/04/06  at  04:49 PM