Bombardier beetles are ground beetles which are most notable for the defense mechanism that gives them their name: when disturbed, they eject a hot noxious chemical spray from the tip of their abdomen, with a popping sound.
The spray is produced by a reaction between two chemical compounds, hydroquinone and hydrogen peroxide, stored in separate reservoirs in the beetle‘s abdomen and mixed when needed in a third chamber with water and catalytic enzymes. Heat from the reaction brings the mixture to near the boiling point of water and produces gas that drives the ejection. The damage caused can be fatal to attacking insects and small creatures and is painful to human skin. Some bombardier beetles can direct the spray over a wide range of directions.
Bombardier Beetle Defies Evolution