Bombardier Beetle 40D0039154

Bombardier Beetle (genus Brachinus)

Bombardier Beetles are ground beetles (Carabidae) in the tribes Brachinini, Paussini, Ozaenini, or Metriini - more than 500 species altogether, that are most notable for the defense mechanism that gives them their name: when disturbed, the beetle ejects a noxious chemical spray in a rapid burst of pulses from special glands in its abdomen. The ejection is accompanied with a popping sound.

A Bombardier Beetle produces and stores two reactant chemical compounds, hydroquinone and hydrogen-peroxide in separate reservoirs in the rear tip of its abdomen. When threatened, the beetle contracts muscles that force the two reactants through valved tubes into a mixing chamber containing water and a mixture of catalytic enzymes. When combined, the reactants undergo a violent exothermic chemical reaction raising the temperature to near the boiling point of water. The corresponding pressure buildup forces the entrance valves from the reactant storage chambers to close thus protecting the beetles internal organs. The boiling, foul-smelling liquid partially becomes a gas (flash evaporation) and is expelled through a outlet valve into the atmosphere with a loud popping sound. The flow of reactants into the reaction chamber and subsequent ejection to the atmosphere occurs cyclically at at a rate of about 500 times per second and with the total pulsation period lasting for only a fraction of a second. The damage caused can be fatal to attacking insects and small creatures and is painful to human skin.

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