Have you ever thought an insect the size of a penny could spray a boiling hot solution at you? Well a bombardier beetle can! There are two large glands that open at the tip of the abdomen. Each gland is composed of a thick walled vestibule which contains a mixture of chemicals produced by the secretory cells and an aqueous solution of hydroquinone and hydrogen peroxide. When the beetle feels threatened it opens a valve which allows the solution from the reservoir to reach the vestibule.
The released energy raises the temperature of the mixture to near 212 °F, vaporizing about a fifth of it. The resultant pressure buildup forces the entrance valves from the reactant storage chambers to close, thus protecting the beetle’s internal organs. The boiling, foul-smelling liquid is expelled violently through an outlet valve, with a loud popping sound. The beetles’ glands store enough hydroquinone and hydrogen peroxide to allow the beetle to release its chemical. They spray roughly 200 times per second, irritating the eyes and respiratory system of the enemy and in some cases killing the predator. So even though this beetle is so small, it has a lot of amazing complexities in its tiny world.
