The bombardier beetle belongs to the ground beetle family (Carabidae) ranging from 1.2 to 1.8 cm long. This beetle is found in North America, South America, Europe, Africa and Australia. Most bombardier beetles are carnivorous and hunt on the ground or in trees. The larvae feed on other insects. They are found in undisturbed riverbanks and floodplains.
This insect possesses a unique method of defense: it sprays predators with hot corrosive liquid that is under pressure. Within its abdomen the beetle has two chambers. One contains a mixture of hydrogen peroxide and hydroquinone; the other contains a mixture of the enzymes catalase and peroxidase. When threatened, the beetle mixes the contents of these two chambers. The enzymes catalyze the decomposition of hydroquinone and hydrogen peroxide to water, p-quinone and oxygen. The heat generated from the reaction brings the mixture to boiling, building up pressure that results in the mixture being expelled explosively from the chamber. The oxygen generated by the reaction acts as a propellant, causing the mixture to pop out of the abdomen through the abdominal tip, which can be aimed by the beetle. A single beetle can discharge up to 29 consecutive times and can spray at a distance of up to 4 times its body length.