Bombardier Beetles Defend Themselves With Mace-Like Substance [Video]

Bombardier beetles have a defense mechanism that deters all but the most persistent predators, having the ability to expel a noxious, mace-like substance from two glands located at the bottom of their abdomen. It might look to the casual observer of the bombardier beetle, upon being on the receiving side of one of the blasts that the beetles can emit, as if the mace-like fluid that they spray out comes from their bottoms, but that is not really what happens, according to researchers from Massachusetts Institute of Technology (MIT) and the University of Arizona. Their findings have recently been published in the Science journal. A video of what occurs is below.

Bombardier beetles, at any rate, the Brachinus Elongatulus ones studied in the most recent study conducted by the researchers from MIT and the University of Arizona, look sort of like ants that are carrying ticks on their backsides. The researchers examined over 500 live bombardier beetles, all from from southern Arizona, and recorded 30 expulsions of noxious spray from 14 of the insects.

Bombardier Beetle Mace Combination of Two Substances

The mace-like substance that bombardier beetles expel is a combination of two different substances. The chemicals that the bombardier beetles mix within their bodies are hydroquinone and hydrogen peroxide. Together, these two chemicals produce benzoquinone. The chemicals are created by and stored in glands underneath the abdomen.

The rancid-smelling quinones beetles produce are ordinarily just used to help harden their exoskeletons. Bombadier beetles, though, have developed a way to also use the quinones as a means of defense.

Hydrogen peroxide and water decompose inside of the bombardier beetles, according to an article at the Clapway site. The decomposition is facilitated by catalases and peroxidases lining the vestibule wall, where valves are also located.

When the research team used X-ray imaging to study how the bombardier beetles mix the two substances to create the mace-like benzoquinone, they discovered that the two chemicals get mixed within a protective layered chamber located inside of the abdomens of the beetles. The recordings that the researchers made were shot at a rate of 2,000 frames per second.

The two substances within the chamber are brought to almost a boil by the heat generated by the chemical reaction that occurs before they are released with explosive force. The explosive force also creates an often somewhat loud popping sound.

The mace-like benzoquinone that the bombardier beetles emit can prove to be fatal to some of the insects that are sprayed with it, and it can be harmful to human skin if it is not washed off. It can irritate the eyes and respiratory systems of whatever insect or other creature gets sprayed by it.

Besides being found in Arizona, where the study published in Science took place, bombardier beetles can also be found on every continent of the world, other than Antarctica. They are ground beetles, and particularly like to live in grasslands and woodlands, which are ideal places for them to lay their eggs.

The researchers involved in conducting the study were Wendy Moore from the University of Arizona as well as Christine Ortiz and Eric Arndt from MIT. According to Wendy Moore, before the study that they conducted researchers had thought that the explosive “pulses” generated by the bombardier beetles “were caused by muscle contractions or by a fluttering of the exit duct during the explosions.”

Wendy Moore added that “the expansion membrane of the reaction chamber,” which “acts as a passive closure mechanism,” and which “varies between female and male beetles,” had never “been described or even predicted before this study.”

At last, thanks to the research conducted and published in Science, the precise way that bombardier beetles defend themselves by spraying out the mace-like substance, benzoquinone, has been discovered. The beetles are like walking chemistry labs, and when two chemicals that they store in glands combine, a reaction occurs, generating enough heat to expel noxious benzoquinone and serve as an effective defense against anything that tries to eat them. A video showing exactly what happens is below.