Brachinus

Brachinus is a genus of predatory ground beetles belonging to the family Carabidae. These beetles are commonly known as bombardier beetles due to their distinctive defense mechanism. When threatened, Brachinus species can eject a hot, noxious chemical spray from the tip of their abdomen. This spray is a mixture of hydrogen peroxide and hydroquinone, which react explosively when expelled, producing a popping sound and a cloud of steam.

The genus Brachinus is distributed across the world, with most species found in temperate and tropical regions. They are typically found in open habitats such as grasslands, fields, and along roadsides. Brachinus beetles are nocturnal predators, feeding on other insects, insect larvae, and other small invertebrates. Their larvae are often parasitic, developing within the egg cases of grasshoppers or other orthopteran insects.

The defensive spray of Brachinus beetles has been a subject of scientific study due to its complex chemical and physical properties. The beetle has specialized glands that store hydrogen peroxide and hydroquinone separately. When needed, these substances are mixed in a reaction chamber with catalytic enzymes, leading to a rapid exothermic reaction that propels the hot spray. This mechanism is highly effective in deterring predators.