How This Beetle Shoots a Jet of Superheated Liquid Out of its Bum

By Sarah Zhang on at

You do not want to piss off the bombardier beetle. When disturbed, it sprays noxious, near-boiling liquid out of its abdomen—an effective though confounding ability. After all, how does the beetle pull off such a violent chemical reaction without, well, damaging its insides?

A newly published study in Science sheds some light the bombardier beetle’s peculiar defence. Although the beetle has been photographed and videotaped, no one had bothered yet to peer inside, where the action really happens.

The research team used high-speed synchrotron X-ray imaging to see inside the beetles at 2,000 frames per second. The beetles create their spray by mixing two chemicals inside a protective chamber in their abdomens. Its internal plumbing is key to allowing the beetle to weather the speed of the explosion unscathed:

The X-ray images of the explosion reveal the dynamics of vapour inside the beetles’ abdomens. They show that spray pulsation is controlled by the passageway between two internal chambers; two structures control this process: a flexible membrane and a valve.

The opening and closing of this passageway between a chamber holding the precursor liquid and an explosion chamber seems to take place passively; an increase in pressure during the explosion expands the membrane, closing the valve. Then, after the pressure is released when the liquid is ejected, the membrane relaxes back to its original state and the passage reopens, allowing the next pulse to form.

Pretty complex for a little beetle, huh? These insights may one day inspire blast-protection systems, the researchers say.

[Science, MIT]