The Beetle That Fires From Inside A Toad
A bombardier beetle mixes two chemicals inside its body and fires them out at around 100 °C, in bursts of up to 500 pulses a second. Swallow one, and it fires from inside your stomach: in a 2018 study, 43% of toads vomited the beetle back up alive, up to 107 minutes later.
A Chemical Weapon Smaller Than A Coin
The bombardier beetle is a ground beetle you could cover with a coin, and it carries one of the most violent defences in the insect world: a spray of boiling chemicals, fired with an audible pop, that burns skin and stings eyes. Pick one up with bare fingers and you will find out why almost nothing eats it twice.
Two Chemicals, One Explosion
The beetle stores two ingredients separately inside its abdomen: hydroquinone and hydrogen peroxide. When threatened, it squeezes them into a hardened reaction chamber lined with enzymes. The reaction is violently exothermic — the mixture is converted into irritating benzoquinones, gases build pressure, and the temperature climbs to roughly 100 °C, the boiling point of water.
Five Hundred Pulses A Second
The spray is not one continuous jet. Valves at the chamber open and close so fast that the beetle can fire in bursts of up to about 500 pulses per second, aiming the nozzle at whatever is attacking it. Each discharge comes with a detonation you can hear, and a single beetle can fire upward of twenty times before its glands run dry.
What It Does To You
The spray is not lethal to a human, but benzoquinone is highly irritating to skin, eyes and airways. Handling bombardier beetles can leave burns and irritation on the skin, and the chemicals sting the eyes and catch in the throat. For a predator the size of a mouse or a frog, the same blast is a mouthful of boiling, toxic gas.
Swallowed Whole — And Then The Twist
Toads do not chew. A Japanese common toad simply gulps a beetle down in one movement, which should be the end of the story. In 2018, Shinji Sugiura and Takuya Sato at Kobe University fed bombardier beetles (Pheropsophus jessoensis) to two toad species and recorded what happened next. The beetles fired their boiling chemicals from inside the toad’s stomach, and 43% of the toads vomited them back up — between 12 and 107 minutes after swallowing them. Every vomited beetle was still alive and active, and one lived on for more than eighteen months afterwards.
The Loop
Boiling spray on your skin, or boiling spray inside a toad: the bombardier beetle’s answer to being attacked is the same, and in almost half the cases, it walks away from the inside of a predator.
Sources
- royalsocietypublishing.org — Successful escape of bombardier beetles from predator digestive systems (Biology Letters, 2018)
- nature.com — Bombardier beetle lives on by causing indigestion
- pnas.org — Spray aiming in the bombardier beetle: photographic evidence
- mcgill.ca — Do Not Mess with a Bombardier Beetle!
- nationalgeographic.com — Bombardier beetles, facts and photos
