Insects


About 75% of the world’s animals are insects. They have been living on earth for over 400 million years, long before humans appeared. Insects have changed a lot and adapted to new climates in order to survive. Today, there are about one million different species of insects and scientists are discovering new groups daily. Insects have different sizes and body forms. Most of them are very small but they can grow as large as 30 cm. Among the most common insects are flies, beetles, bees, butterflies, moths and wasps.

 

Where insects live

Insects live in every region of the world. They can survive in any type of climate, from tropical rainforests to icy polar regions, as long as they can find food. The oceans are the only places where few insects live. Because they are so small, they can live in places where other animals cannot survive, some even live in underground caves.

 

Physical features

Insects belong to a group of animals called arthropods. They do not have a skeleton but a kind of shell that protects them. This exoskeleton is very tight and does not grow with the insect. When an insect becomes too large for the shell it breaks open and a new shell develops.

Insects have three major body parts: head, thorax and abdomen. They have six legs and at least one pair of feelers.

An insect’s antennae, mouth and eyes are located in the head. The compound eyes consist of up to 4,000 separate lenses that combine images inside an insect’s brain. Such a complex eye gives it extremely good eyesight. Insects use antennae to smell and feel. If their feelers are damaged they become helpless.
The thorax has three pairs of legs and two pairs of wings, however, some insects have no wings at all.

The abdomen is the largest part of an insect. It contains organs that digest food, release waste and let insects reproduce.

Body parts of an insect

Body parts of an insect

 

How insects behave

Insects protect themselves from enemies in many ways.  Some can blend into their surroundings by changing their colours. Others, like beetles, have a hard shell that protects them. Some insects produce poison and inject it into enemies by biting or stinging them.

Most insects live alone but there are some social insects that live in colonies. Termites, ants and bees are examples of insects that live in groups of thousands or even millions, in which everything is organized and each insect has a certain task. Such a society is headed by a leader, a queen or a king, whom others follow.
Insects eat plants, animals and other organisms. They also live on other animals and get food from their body. Such insects are called parasites.

Certain insects migrate during the wintertime. The monarch butterfly, for example, flies south to tropical and subtropical areas. In spring they come back to their original habitat.

 

Life cycle of insects

Most insects are born from eggs. Their covering or shell cannot grow and they break out of it after a certain time. After that an insect grows a new shell. This process is called moulting. An insect can moult many times until it becomes a fully grown adult. This process, from hatching out of an egg to becoming an adult, can take between a few days and many years. As an adult, most insects live only for a short time. But there are a few, like the queen of a termite colony, which can live for many years.

Some insects change completely during the different stages of their life. This is called metamorphosis. After hatching from an egg they become a larva, which takes on a wormlike shape. A larva eats a lot and moults several times during its development process. After growth an insect becomes a pupa. It spins a protective covering around itself. During this resting stage an insect develops wings and legs and other body features. In the final stage an adult emerges from the pupa. Bees and butterflies grow in this way.

How a fly develops

How a fly develops

 

Insects and humans

Insects can be helpful to humans in many ways. They eat other insects and dangerous animals that may endanger fields and crops. They keep our environment clean by eating animal waste and other unwanted substances. Some produce valuable products like honey and silk. Flowers, fruits and other plants depend on insects to help spread pollen.  On the other side, insects are an important source of food for birds, frogs and other animals.

There are very few harmful types of insects, but they can do a lot of damage. Some of them spread diseases by stinging and biting people. In tropical regions insects are the main carriers of malaria or the plague. They injure pets and animals, and do damage to trees and crops.

 

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Words

  • adapt to = get used to
  • adult = here: fully grown animal
  • antenna  = one of two long thin parts on an insect’s head, which it uses to feel
  • appear = show up; come to life
  • beetle = an insect with a round hard back, which is usually black
  • blend into = to match with the world around you so that you cannot be seen
  • carrier = here: animal or plant that can spread things to other places
  • cave = a natural hole in the side of a hill or under the ground
  • certain = special
  • colony = group of animals that live together
  • common = widespread
  • completely = totally
  • complex = consisting of many different parts
  • compound = consisting of many parts
  • consist of = are made up of
  • covering = hard skin
  • crops = a plant, like wheat and rice, which is grown by farmers and sold as food
  • damage = destroy
  • depend on = need
  • develop = grow
  • development process = here: the time during which something grows
  • digest = change food into substances the body can use
  • discover = find for the first time
  • emerge = come out of
  • endanger = put in danger
  • enemy = here: animals that want to hurt them
  • environment = the world around us
  • eyesight = the ability to see
  • feature = part
  • follow = go after
  • habitat = living area
  • harmful = dangerous
  • hatch = break out of a shell
  • head = lead
  • however = but
  • humans = people
  • icy = very cold
  • injure = hurt
  • lens = the clear part inside your eye that focuses so you can see things clearly
  • migrate = move to live and eat somewhere else
  • moth = an insect that is related to the butterfly; it flies at night and eats holes in cloth
  • moult= to lose old skin and grow new skin
  • organ = part of the body that has a certain job to do
  • organism = here: living things
  • plague = disease that causes death and spreads  quickly to a large number of people
  • poison = substance that can lead to death or a serious illness
  • pollen = fine powder  which plants produce and which is carried to other flowers and plants by insects
  • process = development , way of growing
  • protect = guard, defend
  • release = let free
  • reproduce = to have babies
  • resting stage = time during which it does not grow
  • scientist = person who works in a laboratory and is trained in science
  • separate = different
  • shape = form
  • shell = hard skin
  • silk = smooth soft cloth made from material that is produced by the silkworm
  • skeleton = structure  consisting of all the bones of the body
  • social = group
  • source = where something comes form
  • species = a group of animals or plants that are almost the same and can have babies together
  • spin = here: to produce skin
  • spread = here: bring from one place to another
  • stage = phase, period, time
  • sting = to make a very small holes in your skin and you feel a sharp pain
  • substance = material
  • surroundings = the world around us
  • survive = live on, exist
  • task = job
  • termite = insect that eats and destroys  wood from trees and buildings
  • thorax = the part of an insect’s body between its head and abdomen
  • tight = stiff, fixed, not flexible
  • valuable = expensive
  • wasp = a thin black and yellow insect that can sting you
  • waste = the solid material that comes out of your body