A beetle mixes two chemicals in its own body to fire a scalding, corrosive spray

The bombardier beetle stores hydroquinone and hydrogen peroxide in separate internal chambers and, when threatened, combines them with enzymes in a reaction chamber that heats the mixture to around 100 degrees Celsius before expelling it as a pulsing, audible spray. The reaction is fast and controlled enough that the beetle doesn't harm itself, and it can aim the spray in almost any direction to drive off ants, frogs, or birds.

— Thomas Eisner, The Bombardier Beetle and Its Use of Gases — Journal of Insect Physiology, 1958