Was It Designed?

The Beetle’s Pressure-Spray System

▪ Though less than an inch in length [2 cm], the bombardier beetle is noted for its unique defense mechanism. When threatened, the insect sprays boiling, foul-smelling liquid and steam from its posterior, warding off spiders, birds, and even frogs.

Consider: This beetle is equipped with “a pair of glands which open at the tip of [its] abdomen.” Each of these has a reservoir that stores an acidic compound and hydrogen peroxide as well as a reaction chamber filled with enzymes dissolved in water. To protect itself, the insect can squeeze the solution from the reservoirs into the reaction chambers to trigger a chemical reaction. The result? Noxious chemicals, water, and steam​—at a temperature of about 212 degrees Fahrenheit [100°C]—​are sprayed onto an attacker. The chambers are less than a sixteenth of an inch [less than 1 mm] long, yet the beetle can change the speed, direction, and consistency of its toxic spray.

Researchers have studied the bombardier beetle to learn how to develop more effective and ecologically-sound mist systems. They have discovered that the beetle not only uses one-way inlet valves to allow chemicals into the reaction chambers but also has a pressure-relief valve to expel them. Engineers hope to use spray technology based on the bombardier beetle in car engines and fire extinguishers, as well as in medical drug-delivery devices, such as inhalers. Professor Andy McIntosh of the University of Leeds, England, says: “Nobody had studied the beetle from a physics and engineering perspective as we did​—and we didn’t appreciate how much we would learn from it.”

What do you think? Did the bombardier beetle’s complex system of valves, combustion, and explosion develop by chance? Or was it designed?

[Picture Credit Line on page 18]

Oxford Scientific/​photolibrary