Brachinus fumans
American bombardier beetle

Bombardier beetles can be found on most continents around the world, but the particular species chosen for this report is found only in North America. Bombardier beetles of all types generally live in temperate zone woodlands or grasslands (Isaak 1997; Salleh et al. 1999).

Bombardiers can inhabit a fairly wide variety of environments as long as there is sufficient moisture to allow for good places to lay their eggs. Bombardier beetles of all types generally live in temperate zone woodlands or grasslands (Isaak 1997, Salleh 1999).

Like all members of the insect order Coleoptera, the bombardier beetle has two elytra (sheaths) over its wings, although the wings themselves are considered vestigal in the American species, and rather useless for flying. To compensate for this inability to escape by flying away from predators, the beetle possesses a rather interesting apparatus for defending itself against predators, which will be elaborated on later. All of the other characteristics of insects in general (six legs, two antennae, body segmented into head, thorax, and abdomen, etc.) are present (Isaak 1997).

The main reason the bombardier beetle is so notable is due to the two small glands located near the end of its abdomen. One gland produces hydrogen peroxide, one gland produces hydroquinone. The two chemicals are mixed in what is evocatively called the "explosion chamber" and have two enzymes, catalase and peroxidase, added to them. These enzymes speed up the reaction to a level where the beetle can make an audible "pop" as it ejects the now-boiling chemical stream at whatever unlucky predator happened to disturb it. Added to this, the beetle can rotate the end of its abdomen 270 degrees in any direction, which allows for an impressive "firing range." In effect, the beetle can spray in whatever direction the predator comes from, a decided advantage (Dawkins 1985; Eisner 2000; Salleh 1999).

A member of the family Carabidae, more commonly known as the ground beetles, the bombardier beetle quite naturally shares some of the habits of its family, and like most other ground beetles tends to come out at night to prey on smaller insects. Unlike most other ground beetles, however, the bombardier is rather gregarious, so when not wandering around looking for food (usually during the day) it will congregate with others of its kind in dark, damp places such as hollow logs (Eisner 2000; Shetlar 1988).

This species, like nearly all the species in the family Carabidae, is a predator, and eats a number of other insects that are agricultural pests. (Shetlar, 1988)

Most of the scientific research done on the beetle has focused on its defense structures, so the question of how it fits into the larger ecological picture in its particular environment is not very well known. It is widely distributed across North America, though rarely found in large numbers.

The defensive structures of the bombardier beetle have been the subject of debate between creationists and evolutionary biologists. Some "creationists" have claimed that the complex defensive spray mechanism of the bombardier beetle is too complex to have evolved naturally. They say such a thing must have been created by a higher intelligence. Evolutionary biologists have discredited this argument, and have presented reasonable explanations for how the structures could have evolved from simpler chemical glands. (Dawkins, 1985; Isaak, 1997)