Beetle’s toxic, explosive vapor explained

With a hot, mighty blast from the rear, bombardier beetles ward off predators with a harmful spray. And now scientists understand how the insects fire off the harmful fog.

Using X-ray imaging, scientists monitored a two-chambered gland in the beetle’s rump. There, a chemical cocktail trickles from a reservoir chamber into a reaction chamber through a valve. In the reaction chamber, the cocktail causes a chemical explosion and forms toxic compounds, called p-benzoquinones. The force of the blast closes off the valve, ensuring a controlled eruption, and propels the noxious spray out of the beetles’ behind in pulses, scientists report in the May 1 Science.

The bursts of fiery mist which can get up to 100° Celsius, are a defense mechanism unique to bombardier beetles.