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The internal organs of a tiger beetle The internal organs of a tiger beetle Insects belong to a group of invertebrates (animals without backbones) called arthropods. Instead of having an internal skeleton, arthropods have a hard outer skeleton. This is made of a light, strong material called chitin that supports and protects their soft inner parts. All insects have six legs and a body divided into three sections or segments: the head, thorax and abdomen. Insects have a pair of long sense receptors on their heads, called antennae. Flying insects have either one or two pairs of wings. Many insects are plant-eaters, but others are carnivorous, feeding on other insects or small animals. An insect's mouth shape reflects its diet: some have tube-like mouths for sucking up fluids; others have jaws for chewing up their food.


Body parts

The body parts of an insect (a parasitic wasp)The body parts of an insect (a parasitic wasp)Insect skeletons are found on the outside of their bodies—unlike ours, which are on the inside. Called exoskeletons, they form a protective armour around the soft parts inside. The insect breathes through tiny holes, called spiracles, in the sides of its body. The hard covering of the legs is jointed to enable the insect to move. Tiny bristles on the legs and body can feel vibrations caused by sound or movement. The insect's foot is called the tarsus. The claw is used for gripping surfaces.

Like its legs, an insect’s antennae are made up of jointed sections. They are highly sensitive to smells, flavours and touch. The insect uses them to detect its food and to sense objects. Ants, for example, use their antennae to pass on “messages” to each other.

There are more species of insects in the world than all other animal species put together. Over 1 million species are already known to us, but scientists estimate there may be between 5 and 10 million insect species yet to be discovered.

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