Bombardier Beetle: The Insect That Fires a Boiling-Hot Spray
Bombardier beetles defend themselves with a chemical explosion. When attacked, they mix stored chemicals in a reaction chamber in their abdomen and fire a spray that comes out near the boiling point of water. Some species fire it in rapid pulses and can aim it in almost any direction.
Quick Facts
- Group: Ground beetles, several hundred species worldwide
- Weapon: A hot chemical spray from the tip of the abdomen
- Temperature: Near 100°C (212°F)
- Speed: Hundreds of pulses per second in studied species
- Found: Every continent except Antarctica
How Does a Bombardier Beetle Spray?
The beetle stores hydroquinones and hydrogen peroxide together in a reservoir. When it is threatened, a valve lets them into a separate reaction chamber lined with enzymes. The reaction releases a sudden burst of heat and gas, and the hot spray blasts out of the beetle's rear.
Pulses and Aim
In studied species, the spray is not one squirt but a rapid series of pulses, hundreds per second. Pulsing lets the chamber cool between bursts. Some bombardiers can swivel the tip of the abdomen to aim forward, backward and even over their own backs.
Swallowed, Then Spat Out
In a 2018 lab study, Japanese scientists watched toads swallow a bombardier species called Pheropsophus jessoensis. Many toads later vomited the beetles back up, sometimes after more than an hour, and the beetles that came out were still alive.
Frequently Asked Questions
Is a bombardier beetle spray dangerous to people?
It can sting and stain skin, but it is not dangerous to people. It is meant to drive off insects, spiders, frogs and toads.
How hot is a bombardier beetle's spray?
It comes out near the boiling point of water, about 100°C.
Where do bombardier beetles live?
They are found on every continent except Antarctica.
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Sources
- Arndt et al. 2015, Science: how the reaction chamber works
- MIT News: the pulsed spray explained
- Sugiura and Sato 2018, Biology Letters: beetles escaping from toads
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Cover photo: Udo Schmidt via Wikimedia Commons, CC BY-SA 2.0.