Bombardier beetle
Bombardier beetles are adephagan ground beetles (Carabidae) in the Brachininae or Paussinae subfamilies—more than 500 species altogether—which are most notable for the defense mechanism that gives them their name: when disturbed, they eject a hot, noxious chemical spray from their pygidial glands with a popping sound. The spray is produced from a catalyzed reaction between hydroquinone and hydrogen peroxide, an aqueous solution of which is stored in the pygidial glands in the beetle's abdomen.