Bombardier beetle

From Wikipedia, the free encyclopedia

Bombardier Beetles are ground beetles (Carabidae) in the tribes Brachinini, Paussini, Ozaenini, or Metriini—more than 500 species altogether—that are most notable for the defense mechanism that gives them their name: They can fire a mixture of chemicals from special glands in their abdomen.

Bombardier beetles

Brachinus species

Scientific classification

Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Coleoptera
Family:	Carabidae

Tribes

Brachinini
Paussini
Ozaenini
Metriini

Wikispecies has information related to:

Brachinini

Australian Bombardier Beetle (Pheropsophus verticalis)

Bombardier beetles store two separate chemicals (hydroquinone and hydrogen peroxide). When they are threatened, the two chemicals are squirted through two tubes, where they are mixed along with small amounts of catalytic enzymes and undergo a violent exothermic chemical reaction. The boiling, foul-smelling liquid partially becomes a gas (flash evaporation) and is expelled with a loud popping sound.

1 Defense mechanism
2 Creationism and Bomby the Bombardier Beetle
3 Darwin's experience
4 References
5 External links

[edit] Defense mechanism

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 catalases 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 can be fatal to attacking insects and small creatures and is painful to human skin.

[edit] Creationism and Bomby the Bombardier Beetle

The young Earth creationist Duane Gish, assistant director of the Institute for Creation Research, described the bombardier beetle in his 1977 book Dinosaurs: Those Terrible Lizards, claiming they could not conceivably have evolved the various components needed to make the system work, as the components appeared to him to provide no benefit in themselves and therefore the entire system would have to be created at once.

He stated that the hydrogen peroxide and hydroquinone would explode on contact, and that the beetle adds an inhibitor to keep this from happening. Then, when threatened, the beetle "squirts in an anti-inhibitor" to start the reaction. As we now know, this is not quite accurate as the beetle instead uses catalysts to cause the reaction to start. Gish blamed a problem of translation leading him to misunderstand his German source, but continued to use his description in debates.

At the end of 1980 the National Center for Science Education - a non-profit organization in Oakland, California, affiliated with the American Association for the Advancement of Science, which defends the teaching of evolutionary biology and opposes the teaching of religious views in science classes in public schools - described the error as well as describing how the mechanism could have gradually evolved through natural selection.^[1] This description of the process was used in publications by other authors, from 1981 to 1990.^[2]^[3]

A similar argument is set out in the children's book Bomby the Bombardier Beetle (ages 4–8), published by the Institute for Creation Research in June 1984, and still on sale as of July 2007.^[4]^[2]^[3]^[5]

In his 1996 book Darwin's Black Box Michael Behe presented the same argument as irreducible complexity which he claimed to have found in various organisms. He discussed the bombardier beetle, but agreed that Darwinian evolution may possibly have been responsible for the formation of the Bombardier Beetle defensive system, as well as creationism.^[3]

[edit] Darwin's experience

During Charles Darwin's education at the University of Cambridge he became involved in a national craze for the competitive collecting of beetles. On one occasion in 1828 he stripped bark from a dead tree and caught a rare beetle in each hand, then saw another new species. With the habits of an egg collector, he popped the beetle from his right hand into his mouth and grabbed the other with his free hand. The beetle which he had placed in his mouth, likely a bombardier beetle, "ejected some intensely acrid fluid, which burnt [his] tongue," forcing him to spit it out; he lost the beetle, as well as the third one.^[6]