This Badass Beetle Can Really Blow Off Steam
Bombardier beetles are experts at chemical warfare. Though many insects use chemicals to defend themselves, the bombardier’s firepower earns it the top rank. When threatened, these aptly named bugs detonate explosions within their bodies and blast their attackers with boiling caustic bombs.
A pair of glands in the beetle’s abdomen functions as a portable chemistry lab, storing volatile chemicals in separate compartments and mixing them together just prior to launch. Each gland is divided into two chambers—a reservoir chamber and a reaction chamber—connected by a one-way valve.
Mixing it Up
The reservoir chamber contains a solution of hydrogen peroxide and hydroquinone, a chemical common in skin-bleaching treatments. When the bombardier beetle senses danger, the muscles surrounding this reservoir contract, pushing a liquid bead through the valve and into a rigid-walled reaction chamber.
Enzymes stored in this second chamber spark a violent reaction that generates intense heat and produces oxygen, water vapor, and irritating chemicals called benzoquinones. Pressure from the expanding water vapor and oxygen gas propels the chemical concoction through an exit nozzle at the beetle’s rear end, spraying assailants with toxic fluids and scalding steam traveling at roughly 22 miles per hour.
The scorching spray can be lethal for smaller foes, like ants, and causes painful burns for larger predators. Igniting internal explosions is undoubtedly dangerous, but the reaction chamber’s rigid walls contain the chemical reactions and prevent the beetles from blowing themselves to bits.
Firing at Full Blast
To the naked eye, each blast from the beetle’s bum appears as a single stream, but every ejection is actually a succession of high-speed pulses—more akin to a rapid-fire squirt gun than a gushing fire hose. Scientists suspect the pulsing action allows the reaction chamber to cool down between rounds and protects the beetle from cooking itself.
Some species of bombardier beetles can twist their exit nozzles like tank turrets to locate the best angle of attack or to confront their enemies head-on. The African bombardier beetle (Stenaptinus insignis) can even maneuver its rear to take aim at ants that climb onto its back.
Fighting For Their Lives
The beetles have fuel for numerous blasts, but most enemies retreat long before the ammunition runs dry. The unlucky predators that swallow the beetles may regret their snack choice, because these tenacious bugs don’t give up without a fight.
In laboratory studies, toads that consumed bombardier beetles suffered super-sized stomachaches. The ingested bugs quickly unleashed their chemical arsenal, blasting the bewildered toads’ bellies with burning chemicals until they vomited. Despite dripping in digestive juices, the victorious beetles emerged unharmed and survived to fight another day.
To read more about some other menacing insects, check out this article.
