Bombardier beetle
|
|
| Bombardier beetles | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Scientific classification | ||||||||||
| ||||||||||
| Tribes | ||||||||||
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 posterior.
The mechanism works thus: 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 reservior 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 is fatal to attacking insects and painful to human skin.
Intelligent design
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. The book argues that the beetles' internal design, in which certain chemicals must be mixed in certain ways at certain times to produce tiny explosions, is an example of irreducible complexity, and therefore the product of intelligent design.
However, some researchers have shown that their chemical weapon involves minor alterations of other, less noxious beetles.
Further reading
- Bomby the Bombardier Beetle, by Hazel Rue, ISBN 0932766137
External links
- Bombardier Beetles and the Argument of Design, from the the talk.origins archive (http://www.talkorigins.org/faqs/bombardier.html)
- Proceedings of the National Academy of Sciences article: "Spray aiming in the bombardier beetle: Photographic evidence" (http://www.pnas.org/cgi/content/abstract/96/17/9705?ijkey=097c98acbdf7a2ee2d340f97a0459336c9f30c84&keytype2=tf_ipsecsha)de:Bombardierkäfer