Beetles:

Largest group of insects

If you were asked which creature dominates the insect world, what would your answer be? Perhaps, many of you would say flies, mosquitoes or even butterflies. But, in reality, the largest order of insects in the animal kingdom, is none other than the order Coleoptera which comprise a wide variety of beetles. Scientists claim that there are between five to eight million beetles with about 350,000 identified or described species.

There are more species of beetles in the world than plants!

Beetles have been around for about 300 million years and since they have the ability to adapt to any type of environment, it is believed that they may continue to exist long after humans have disappeared from Earth.

The order name of these creatures is pronounced as 'co-le-OP-ter-a' and was first used by Aristotle in the fourth century B.C, more than 5,000 years ago. It has been coined using the Greek words koleos which means sheath or shield and ptera which means wings, as these beetles have sheathed wings.

A distinctive feature of this group of insects is their elytra, a reinforced first pair of wings, which act as protective covers for the second pair of wings, and the abdomen.
 

It is this pair of wings (the sheathed wings) which are large and membranous that are used for flying.

The elytra however is of great importance because it is not only used to protect these 'flying' wings, but also to survive. Some species of beetles trap moisture on their inner wings and hold it under the elytra, enabling them to survive in deserts, while some other aquatic beetle species trap air under the elytra, and use it to live underwater.

Beetles are found in almost all habitats around the world, but are not known to exist in the seas and Polar regions. All species have a uniform anatomy which consists of three segments like in all other insects, a head, thorax and abdomen. All three pairs of legs and both pairs of wings extend from their abdomen.

Their mouthparts are similar to that of grasshoppers - chewing type with well developed mandibles; a pair of hard, often tooth-like structures that are used to grasp, crush, cut or fend off enemies.

Two appendages found near the mouth help them to more food into the mouth. The antennae are either thread-like, saw-toothed, comb-like, feather-like or clubbed. They have compound eyes which have remarkable adaptability. In some species especially the aquatic, they are split, allowing them to view both below and above water.

The antennae are the primary organs of smell, but they are used to feel out the environment physically. The legs are multi-segmented (2-5 small segments) and these are called tarsils.

Like in many other insects, they have claws at the end of the last tarsal segment. Insects obtain oxygen via a tarachoal system and beetles do the same. They go through complete metamorphosis.

However, the beetle larvae could be differentiated from that of other insect larvae by their hardened, often darkened head, presence of chewing parts and spiracles along the sides of the body.

Beetles feed on plants, fungi, broken down animal and plant debris, sap of trees, and nectar. Their main enemies are birds and mammals.
 

Even though a majority of the beetles can fly, in some species, this ability is lost and they are considered 'ground' beetles.

Some beetles are considered agricultural pests, but others, such as ladybirds are pest controllers.

The Goliath beetle is not only considered to be the largest in the scarab family of beetles, but also in the whole of the insect world. There may be a few other insects which may be larger, but the Goliath beetle, at 12-13 cm in length and weighing around 115 grams, is probably the largest and heaviest.

There are about 30,000 or more species identified so far and scientists believe more are yet to be discovered. There are five species in the genus. Goliath beetles survive on the sap of trees, fruits and dead plant material. They help to recycle 'used material' to keep the Earth clean. They are known as nature's clean-up crew.
 

All Goliath beetles are found in the African continent and are strikingly patterned. However, one of the most brightly coloured beetles of the scarab family is the Flamboyant fruit beetles or striped love beetle. Its shell seems to have a prismatic quality, the carapace gets a rainbow tint.

These beetles too are found in Africa, mostly in the rainforests, and live on nectar and pollen. The larvae live in decaying wood and feed on dead wood and leaf litter.

Adults grow to about 25 - 40 cm and the trademark Y shaped horn is displayed by males when fighting for a mate. The females have a shovel-like tusk which they use for burrowing wood to lay eggs.

They come in many dazzling colours including green, blue, black or even gold. There are about 20,000 described species in this scarab family and they include the Dung beetle and the Goliath. The Flamboyant flower beetle was considered sacred by the Egyptians; they were honoured by designing pieces of jewellery depicting them and including them in many a folk tale.

The Buprestidae family of beetles, known as Jewel beetles, are also very striking and are treasured by beetle collections. They range from very small to large. Their sizes range from 3mm to an impressive 100mm, but most species are under 20 mm in size. These brightly coloured beetles are called Jewel beetles because of their glossy iridescent colours.

The prize for the longest life history in the insect world goes to the Jewel beetle. The eggs of these beetles, which are spread worldwide, are laid under the bark of the living tree.

Fact file

* Bombardier beetles belong to a group of ground beetles and are found worldwide. Many species are carnivorous. When attacked, these beetles release chemicals into a specially strengthened chamber in the abdomen, which is later released with explosive force from the anus. In some species, the spray is released with an audible pop; the jet of liquid released turns into a gas cloud.
 

* Sexton beetles are known as nature's undertakers. By burying the carcases of small mammals, these beetles effectively 'clean up the environment. They are popularly called the burning beetles. Like flies, Sexton beetles have a very acute sense of smell.

* The Red-brown click beetles, also known as the Skip-jack are common; there are over 10,000 species in the world.

* Fireflies and glowworms are rather nondescript beetles..

* Fregate Island beetles are a uniquely isolated species found only on one small island in the Indian Ocean. The beetle is flightless and the elytra (hardened wing case) are fused along the midline. The elytra are hard and the beetle has been described as 'almost uncrushable'.