Bombardier Beetle

**Bombardier beetles** are ground beetles (Carabidae) in the tribes Brachinini, Paussini, Ozaenini, or Metriini—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 the tip of the abdomen with a popping sound.

The spray is produced from a reaction between two chemical compounds, hydroquinone and hydrogen peroxide, which are stored in two reservoirs in the beetle's abdomen. When the aqueous solution of hydroquinones and hydrogen peroxide reaches the vestibule, catalysts facilitate the decomposition of the hydrogen peroxide and the oxidation of the hydroquinone. 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. Some bombardier beetles can direct the spray in a wide range of directions.

The beetle's unusual defense mechanism is claimed by some creationists to be an example of what they call irreducible complexity, though this is refuted by evolutionary biologists.

## Habitat

Bombardier beetles inhabit all the continents except Antarctica. They typically live in woodlands or grasslands in the temperate zones but can be found in other environments if there are moist places to lay their eggs.

## Behavior

Most species of bombardier beetles are carnivorous, including the larva.[4] The beetle typically hunts at night for other insects, but will often congregate with others of its species when not actively looking for food.

## Anatomy

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 catalases and peroxidases produced by the secretory cells that line the vestibule. Both glands are also made up of a thin-walled and compressible reservoir which contains an aqueous solution of hydroquinones and hydrogen peroxide.

## Secret Weapon

Bombardier emissions range from slow secretions to rapid bursts, hot enough to burn and stain human skin. Their caustic defenses irritate the eyes and respiratory system of predators, often inflicting painful but temporary incapacitation.

Sometimes, their explosive emissions can even save their lives once they've been swallowed. Frogs, for example, have been known to regurgitate bombardiers after realizing the insects weren’t exactly palatable. Creating a boiling-hot chemical bomb inside your body is no easy task. These tiny beetles rely on an elaborate internal network of reservoirs and chambers to synthesize their blasts safely.

The beetle’s explosive power is derived primarily from the mixture of two chemical compounds—hydroquinone and hydrogen peroxide—that are stored in separate reservoirs in the abdomen. The chemicals then pass through a valve before meeting in a special chamber, along with an enzyme that catalyzes the reaction. This creates gases that rapidly expand and give off heat.

Beetles can open and close valves to this reaction chamber rapidly, fast enough to produce up to 500 explosive bursts in a second. These insects can also aim the chemical sprays at prey, using their rear ends like a noxious water pistol.