A toad contemplates a bombardier beetle, which could prove difficult to digest.

A toad regurgitates a bombardier beetle, which can spray the gullets and stomachs of its predators with scalding chemicals. Credit: S. Sugiura & T. Sato/Biol. Lett.

Animal behaviour

Bombardier beetle lives on by causing indigestion

Insect has a superheated surprise for anything that swallows it.

A species of bombardier beetle can survive being eaten by squirting a boiling-hot chemical over predators’ innards, causing them to vomit.

Some bombardier beetles are known to release chemicals heated to about 100 °C from their rear ends when attacked. But whether — or how — this strategy helps them to escape from predators has not been clear. Shinji Sugiura and Takuya Sato at Kobe University in Japan fed the bombardier beetle Pheropsophus jessoensis to two species of toad, Bufo japonicus and B. torrenticola.

Within two hours of the meal, nearly half the toads had regurgitated the insects, which were all alive and well. When toads were fed beetles treated to exhaust their reserves of scalding spray, only 5% of the amphibians spat out their meals, suggesting that the spray helps the beetle to escape from predators.