 Beetles make up about 25% of all known species of animals. Bombardier beetles, like most ground beetles, lay their eggs in small underground tunnels or cracks in rotting wood, and in the decomposing remains of other living things ... which also serve as a food source for the larvae when they hatch. The larvae eat continuously, shedding their skin often as they grow. After molting for the last time, an individual larva metamorphoses into a pupa, which soon sheds its skin and releases the adult beetle. Ground beetles tend to live for several weeks, during which time they mate and lay more eggs. The bombardier beetle, Brachinus fumans, which can be found on most continents around the world, shares the characteristics of other beetles, which are insects: six legs, two antennae, and a body segmented into head, thorax, and abdomen. It also has two wing covers over its wings, like most beetles, but it cannot fly. To compensate for this inability to escape from predators, it has evolved an incredible defense system.   The reason the bombardier beetle is so unique is due to the two small glands located near the end of its abdomen. One gland produces hydrogen peroxide, while the other manufactures hydroquinone. The two chemicals are mixed in an 'explosion chamber', where two enzymes, catalase and peroxidase are added. These enzymes speed up the reaction to the boiling point, and the beetle ejects the boiling chemical stream at whatever predator is nearby. In addition, the beetle can rotate the end of its abdomen 270 degrees in any direction, which makes it operate sort of like a tiny cannon.
The mini-explosions release the boiling fluid in pulses, about 500 every second, which can be heard as a popping noise. The way the beetle fires hot liquid is similar to the pulse jet propulsion mechanism of the German V-1 'buzz-bomb' of World War II. The chemicals that create the hot irritating stream have to be stored separately in the beetle's abdomen because they combine explosively when brought together. |