Bombardier beetle

The Bombardier Beetles are insects of the family Carabidae that possess the ability to fire burning liquids from a specially designed posterior end. There are two main subfamilies of Carabidae that contain bombardier beetles. These subfamilies are Brachininae and Paussinae. There are hundreds of species of bombardier beetles that are all classified together because of their common defense mechanism. This defense mechanism allows the beetles to survive in the wild against other predators.

Bombardier beetles usually grow to be between 1.2-1.8 cm in length. Like all other members of Carabidae, these beetles perform complete metamorphosis to grow from the egg to the adult. In their life of several weeks, they fully mature and die. The various bombardier beetles species live in every continent except for Antarctica. These beetles have sparked many debates between evolutionists and creationists because of their defense mechanisms.

Body Design


Though there are many different species of bombardier beetle, adults usually range in size between 1.2 cm to 1.8 cm. Bombardier beetles of different genera vary in appearance, but they have several common features. The wings of these exoskeleton bearing beetles are protected with a cover called the elytra. Because of this protective covering, the flight abilities of these beetles are drastically reduced. These inadequate flight capabilities force them to rely on other methods of protection. All bombardier beetles are characterized by their unique defense mechanism located in the abdomen (see Defense Mechanism).

The two genera of bombardier beetles each vary in many ways. The bombardier beetles from subfamily paussinae (commonly known as the "flanged bombardier beetle") have a different head and antennae from those in brachininae. The flanged bombardier beetles possess two enlarged antennae. Some of these beetles have glands that secrete chemicals that can fool ant colonies and allow the beetle to invade. In subfamily brachininae, many species such as the brachinus crepitans possess thinner, longer antennae. The brachinus crepitans' elytra are a blue-green color while the head, thorax, and legs are an orange color. Many other organisms in subfamily brachininae have a similar coloration pattern to this.

Life Cycle
The bombardier beetle is similar to all other members of family Carabidae in that it undergoes complete metamorphosis. The eggs are often laid in a safe location that is protected from predators, such as a pile of mud, or dead, decaying plants. Once the larva hatches out of the egg, it immediately begins a pattern of consuming food and molting. Upon the final shedding of its exoskeleton, the larva becomes the pupa, where it continues a similar process as the larval stage. After the final molt of the pupa, the insect becomes an adult.

Members of family Carabidae have an average life span of several weeks. During this time period, the bombardier undergoes metamorphosis from egg to adult. The beetles also have the opportunity to mate during this time. The bombardier beetles of each genus both go through a similar life cycle that may vary slightly depending on the habitat.

Ecology
Various species of bombardier beetles can be located in every continent except for Antarctica (the habitat range map shows only the bombardier beetles of genus brachinus and therefore lacks the locations of species from subfamily paussinae). The species brachinus fumans, lives only in North America while the brachinus crepitans lives in various parts of Europe including central Sweden, southern England, and south Wales as well as parts of northern Africa. The brachinus crepitans mostly lives in coastal locations, but they have been seen in inland locations. Most bombardier beetles prefer to live in temperate forests or grasslands, but the brachinus fumans lives in deserts, savannas, chaparral, and forests. While many species prefer these conditions, bombardier beetles vary greatly in habitat preferences.

Similar to other members of family carabidae, bombardier beetles are carnivorous and feed on insects. In the adult stage, the bombardier beetle tends to hunt either on the ground or in trees. Even in the larval stage, the beetles consume other insects to provide energy for growth. Bombardier beetles are rarely preyed upon because of their defense mechanism (see Defense Mechanism). This defense mechanism often repels predators who attempt to move too close to the beetle.

Defense Mechanism
The most distinguishing feature of the bombardier beetles is the unique defense mechanism that all possess. These beetles have two chambers located in the abdomen, containing different chemicals that when combined, create a spray that reaches temperatures of 212°F. One chamber contains a mixture of hydrogen peroxide and hydroquinone. The other contains enzymes called catalases and peroxidases. When the beetle shoots its spray, the chemicals mix, creating a high pressure, and dangerous burning liquid. The point at the posterior of the insect that shoots the spray is capable of rotating 270 degrees. This characteristic allows the beetle to aim the spray faster and with more ease. When the spray hits a target, a "popping" sound is made from the chemicals. This defense mechanism protects the bombardier beetle from potential predators such as spiders, ants, and frogs.

The bombardier beetle's defensive mechanisms have started many debates between creationists and evolutionists. Creationists have often stated that such a complex and potentially dangerous system could not have simply evolved. If they had evolved, why did the beetles have the two chambers containing these highly reactive substances in the first place? The chemicals have no benefit by themselves. Evolutionists state that the bombardier beetles chambers evolved from minor structures through mutations and survival of the fittest to become the insect’s primary defense mechanism.

Video
This video captures the bombardier beetle in the process of spraying its burning chemicals. Pib9qT-pccI