A team of researchers from MIT, the University of Arizona and Brookhaven National Labs has figured out how the bombardier beetle manages to produces the boiling hot, noxious spray it uses as a defense mechanism. According to the new research, the beetle mixes precursor chemicals inside its body, and the pressure generated by the reaction forces the hot, irritating liquid to eject from the body of the beetle toward its target.
The new research was published in the May 1st edition of the academic journal Science.
More on Bombardier beetle defense mechanism
The irritating liquid the beetles spray is benzoquinone, and is a relatively common defensive agent used by insects. However, bombardier beetles are the only insect known to create superheated liquid and eject it in a powerful, pulsating jet.
The beetles don’t actually synthesize the benzoquinone until just before they use it. They mix two chemical precursors (stored separately) in a chamber in abdomen. As the liquids combine to form the irritating benzoquinone, they also produce intense heat and also generate the pressure required to eject it as a jet spray that can travel several feet.
“For decades, the complex mechanism of how the bombardier beetle achieves spray pulsation as a chemical defense has not been understood, because only external observations were used previously,” notes team member Christine Ortiz (professor of materials science and engineering at MIT). In this study, the researchers applied high-speed synchrotron X-ray imaging to view the internal structures in the abdomens of living bombardier beetles when they sprayed.
The researchers used a lab at the Argonne National Laboratory to produce detailed images that revealed how the process works.
X-ray images of the explosion inside the beetles’ abdomens show that spray pulsation is controlled by the passage between two internal chambers with a flexible membrane and a valve.
The opening and closing of this passage between the chamber holding the precursor liquid and the explosion chamber apparently occurs automatically as an increase in pressure during the explosion expands the membrane, closing the valve. This very rapid internal process had never been directly observed before
Statement from biology professor
R. Jeffrey Dean, a professor of biology at Cleveland State University who studies the bombardier beetle, commented taht the new research is a “wonderful confirmation of the qualitative passive ‘pulse jet’ model” first proposed by his team. “Although the findings are not unexpected, I’m amazed at the progressive advances in techniques,” he continued.