We live in an age of insects. About half of all known animals are insects. Scientists have found about 1 million species (kinds) of insects so far. There are more species of insects than of any other animal in the world. Bees, flies, ants, grasshoppers, beetles, and butterflies are some of the insects that might live near you.
Insects buzz in the air. They crawl over stones. They hop through grass. They dig tunnels underground.
Some insects are helpful. They do important jobs to help plants grow. They help get rid of wastes and dead plants and animals. Some insects are harmful. They bite or sting. They carry diseases or destroy crops.
What Makes an Insect an Insect?
Insects are invertebrates, or animals without backbones. They breathe air through holes in their bodies. The body of an insect has three main parts called the head, thorax, and abdomen.
Insects go through life stages and have very different forms in each stage. Adult insects usually have three pairs of legs, one pair of antennae, and two pairs of wings.
Insects are small animals. You could barely see the feathery-winged dwarf beetle because it is only 1t inch (0.25 millimeters) long. The walkingstick of Southeast Asia is one of the biggest insects. It can be 20 inches (50 centimeters) long with its legs stretched out.
An insect does not have bones. Its body has a hard outer covering. The hard covering is called an exoskeleton, or external skeleton.
Where do Insects Live?
Insects can live almost anywhere on Earth. Insects called rock crawlers live on the cold mountaintops of the Himalayas in Asia. These insects make a kind of antifreeze. The antifreeze works like antifreeze in a car. It keeps water in their bodies from freezing solid.
Some ants live in the heat of the Sahara, a desert in Africa. They look for food even in the hottest weather, when temperatures can be higher than 116° Fahrenheit (47° Celsius).
Many insect species live in the fresh water of lakes, streams, ponds, and swamps. Very few insects can live in the salty water of the oceans.
More insects live in tropical rain forests than any other place in the world. Scientists believe there are millions of insect species living in the rain forest that have not yet been found.
What do Insects Eat?
Insects eat all kinds of foods. Insects that live outdoors eat leaves, wood, nectar from flowers, or other small animals. Insects that live indoors eat wool clothes, glue, and even soap.
Each species of insect has special mouthparts for the type of food that it eats. Some insects such as grasshoppers and beetles have mouthparts for chewing food. Butterflies and moths have a tongue like a drinking tube that they put into a flower to suck up nectar. They roll the tube up when they are not feeding.
Can Insects See and Hear?
Insects do not see the world the way you do. You have two eyes with one lens each. An insect has two bulging eyes on its head. The eyes are made of many lenses and are called compound eyes. Insect eyes cannot see clearly the way your eyes can. But insect eyes can detect very small movements better than you can. This ability helps them catch prey—or escape from animals that prey on them.
Some insects can hear. Most insects do not really hear the way you do. Insects learn about the world around them with feelers or antennae. The antennae extend from the front of an insect’s head. Most insects use their antennae for smelling. Mosquitoes can also use their antennae for picking up sounds.
What are an Insect’s Life Stages?
Most insects start life inside an egg. The animal that comes out of the egg looks different from its parents. It does not have wings. It may not even have legs. As the insect grows, it starts to change shape. This change is called metamorphosis. There are two kinds of metamorphosis, called incomplete and complete.
Dragonflies, grasshoppers, and crickets are some insects that go through incomplete metamorphosis as they grow up. The young insects are called nymphs or naiads. The young insect molts, or crawls out of its exoskeleton, as it grows bigger. It grows a new, larger exoskeleton. Its body changes each time it molts. Soon it gets the shape of an adult insect with wings.
Butterflies, moths, beetles, bees, and flies are insects that go through complete metamorphosis. The young insects are called larvae. They look completely different from their parents. Caterpillars are the larvae of butterflies and moths. Maggots are the larvae of flies.
Larvae change into another stage called the pupa. The pupae of many insects spin a protective case made of silk called a cocoon or a chrysalis. The larva’s body changes completely inside the case. A caterpillar changes into a beautiful butterfly or moth. A maggot becomes a housefly. The adult insect then breaks out of its case. Flying insects pump blood into their new wings and fly away. (Encarta Kids Encyclopedia)