Bombardier Beetle: The Exploding Insect

If there is one thing Mother Nature is good at, it’s coming up with cool defense systems for insects to use. Insects have an incredible amount of survival strategies, such as claws for hunting, powerful jas, camouflage, auditory signals, and even chemical warfare.

By far though, the most hardcore insect is one that shoots literally chemical bombs at its enemies. The aptly named Bombardier beetle is able to spray a corrosive liquid from its abdomen to deter predators and assert dominance. This explosive beetle can produce such noxious fume it can even kill other insects.

Credit: Katja Shulz via Flickr CC-BY 2.0

What Do Bombardier Beetles Look Like?

Bombardier beetles encompass some 500 species of beetle in the Carabidae family. Bombardier beetles range in size from a few centimeters up to two or more inches. Most bombardier beetles have an unusually enlarged abdomen with an elongated head and thorax. Their overall body shape resembles that of ants instead of other common beetles.

Most bombardier beetles have long antennae and short forelegs. The end of the abdomen contains an opening where it stores the chemicals the beetle uses to create its explosions. Their heads contain sharp mouthpieces they use to hunt other insects. 

Credit: David Hill via Flickr CC-BY 2.0

How Do They Make Their Explosions?

Bombardier beetles create their explosions using a mixture of peroxides hydroquinones.  They store these chemicals in two distinct containers in the abdomen. When faced with a threat, the beetle will open a valve allowing the peroxide to flow into the main chamber. Once there, it reacts with a secretion along the interior cell wall, causing a violent exothermic reaction.

This reaction is very powerful and quickly reaches temperatures over 100 degree-C—hot enough to boil water. The beetle then expels this liquid out of an outlet valve on the tip of the abdomen, shooting at whatever threatens it. The beetle is so adept at firing its bombs, it can send over 70 pulses in less than a second.

The caustic liquid can cause burns and is even strong enough to outright kill smaller insects. Even more impressively, the explosion does not harm the beetle in the slightest. A special valve closes off the internal storage chamber when the explosion happens, protecting the beetle’s internal organs. The special design keeps the chemicals stored right until the time the beetle needs them.

A single beetle can fire off its bombs 20 times before running out of fuel. Some species are capable of rotating their abdomens so they effectively have a 270-degree firing range. The typical defense strategy is to fire off a few rounds, stunning the predator and giving the beetle time to unfurl its wings and escape.

Credit: Peter Halasz via WikiCommons CC-BY-SA 2.5

The bombardier beetles’ combustible abilities have been studied by explosion and propulsion experts to find ways to protect people from blasts. Creationists and proponents of intelligent design theories argue that the beetle’s ability is an example of irreducible complexity, but evolutionary biologists dispute such claims.

Whatever the answer to this evolutionary question, one thing is for sure: If you see a bombardier beetle, let it be!