MAY
1992

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

05-14-92

Bombardier Beetles

WEST LAFAYETTE, Ind.
Bombardier beetles are fittingly named. Historically, bombardiers were people who waged war by lobbing a variety of objects at their foes. Bombardier beetles don't drop bombs, but they have maastered the art of chemical warfare.

When these insects are attacked or disturbed they live up to their name. The bombardier beetle ejects a secretion composed primarily of chemcials known as quinones. The quinones are not stored in the insect. They are produced as needed in a complex reaction that would make any chemistry teacher proud.

The reaction, which takes less than a second, produces heat and gaseous oxygen. The gas propels the mixture from the insect with a popping sound. The temperature of the explosion has been shown to reach 100 degrees Celsius, the boiling point of water. Consequently, any creature unlucky enough to raise the ire of a bombardier beetle is spraed with a hot chemical mixture.

Bombardier beetles are not just mad bombers. They are excellent marksmen -- or should we say "marksbeetles?" -- who direct the spray precisely. The gland that produces the defenseive chemicals is located at the tip of the abdomen. The abdomen works like a movable turret that is pointed in the direction of the attack. If an ant attacks a beetle's leg, for example, the beetle "bombards" in that direction.

The chemicals in the beetles' spray are very effective. A toad attempting to make a meal out of a bombardier beetle is rewarded with a moth full of hot chemicals. The amphibian spends the next few moments doing a toad's version of "Yuk," probably thinking seriously about a life devoted to eating insects.

Bombardier beetles really are pacificists in their little insect hearts and will only live up to their name as a last resort. When disturbed, they ty to avoid trouble by running away. If such an evasive technique does not work, they pull out all that stops and employ their chemical weapons. For these beetles "Bombs Away!" is not just a cute saying, it is a matter of survival.

 

Writer: Tom Turpin
Editor: Elaine Lambert