Animal: Beetle

Scientific Name: Numerous, depending on the species

Animal Type: Insect

Habitats: Found in all our habitats except the Ocean

The Beetle:

Beetles are a group of insects which have the largest number of species. There are many thousands of discovered species and constitute about twenty-five percent of all known life-forms. Forty percent of all described insect species are beetles (about 350,000 species), and new species are frequently discovered. Estimates put the total number of species at between 5 and 8 million.

Physical Characteristics:

The general anatomy of beetles is quite uniform, although specific organs and appendages may vary greatly in appearance and function between the many families in the order. Like all insects, beetles' bodies are divided into three sections: the head, the thorax, and the abdomen. When viewed from below, the thorax is that part from which all three pairs of legs and both pairs of wings arise. The abdomen is everything behind the thorax. All three of the major sections of the body are themselves composed of several further segments, although these are not always readily discernible. Beetles are generally characterized by a particularly hard exoskeleton and hard front wings. The beetle's exoskeleton is made up of numerous plates called sclerites, separated by thin sutures. This design creates the armored defenses of the beetle while maintaining flexibility.

In some beetles, the ability to fly has been lost. These include the ground beetles and some "true weevils", but also some desert and cave-dwelling species of other families. Many of these species have the two elytra fused together, forming a solid shield over the abdomen. In a few families, both the ability to fly and the elytra have been lost, with the best known example being the glow-worms, in which the females are larviform throughout their lives.

Beetles have mouthparts similar to those of grasshoppers. Of these parts, the most commonly known are probably the mandibles, which appear as large pincers on the front of some beetles. The mandibles are a pair of hard, often tooth-like structures that move horizontally to grasp, crush, or cut food or enemies. The eyes are compound and may display remarkable adaptability, as in the case of whirligig beetles, in which the eyes are split to allow a view both above and below the waterline. Beetles' antennae are primarily organs of smell, but may also be used to feel out a beetle's environment physically. The legs, which are multi-segmented, end in two to five small segments called tarsi.

Like many other insect orders beetles bear claws, usually one pair, on the end of the last tarsal segment of each leg. Oxygen is obtained via a tracheal system. Air enters a series of tubes along the body through openings called spiracles, and is then taken into increasingly finer fibers. Pumping movements of the body force the air through the system. Beetles have haemolymph instead of blood, and the open circulatory system of the beetle is powered by a tube-like heart attached to the top inside of the thorax.

Food Chain:

Besides being abundant and varied, beetles are able to exploit the wide diversity of food sources available in their many habitats. Some are generalists, eating both plants and animals. Decaying organic matter is a primary diet for many species. This can range from dung, which is consumed by coprophagous species such as certain scarab beetles , to dead animals, which are eaten by species such as the carrion beetles. Some of the beetles found within dung and carrion are in fact predatory, such as the clown beetles, preying on the larvae of coprophagous and necrophagous insects.

Many beetle species, including ladybirds and blister beetles, can secrete distasteful or toxic substances to make them unpalatable or even poisonous. These same species often exhibit aposematism, where bright or contrasting colour patterns warn away potential predators. Large ground beetles and longhorn beetles may go on the attack, using their strong mandibles to forcibly persuade a predator to seek out easier prey. Others, such as bombardier beetles (within Carabidae) spray acidic gas from their abdomen to repel predators.

Habitat features:

Beetles can be found in almost all habitats, but are not known to occur in the sea or in the polar regions. They interact with their ecosystems in several ways. They often feed on plants and fungi, break down animal and plant debris, and eat other invertebrates. Some species are prey of various animals including birds and mammals.

Aquatic beetles use several techniques for retaining air beneath the water's surface. Beetles of the family Dytiscidae hold air between the abdomen and the elytra when diving. Hydrophilidae have hairs on their under surface that retain a layer of air against their bodies. Adult crawling water beetles use both their elytra and their bottom hind legs in air retention while whirligig beetles simply carry an air bubble down with them whenever they dive.