All About Insects Science Grade 3 Learning Concepts | Orchids
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Animals Around Us

Concept: All About Insects

What are insects?

  • Insects are a group of small creatures found around us. This group of the animal kingdom comprises the largest variety of creatures.
  • Their existence is both useful and harmful for humans.
  • Example : Cockroach, ant, honey bee, etc.


Characteristics of insects:

  • They lack a backbone.
  • They have a hard shell-like external structure called an exoskeleton.
  • An insect's body can be divided into three parts—head, thorax, and abdomen.
  • Insects have antennae that are meant for sensing smell and any movement in the surroundings.
  • They have a compound eye.
  • Insects have three pairs of legs and two pairs of wings. The end part of the legs is equipped with claws that can hold any surface tight.
  • They lack lungs, and they exchange gases through holes on their body called spiracles.
  • The sting is a hook-like structure seen at the end of the abdomen. Insects pierce this sting in the body of an intruder when they sense danger. Most insects use this as a defence mechanism. The stings of insects are generally poisonous.

Habitat of insects:

  • Insects are adapted to live in every habitat like land, water, forests, mountains, deserts, etc.
  • The habitat should provide sufficient food resources and appropriate breeding grounds for the insects.
  • Some insects change their habitat based on the phase of their life cycle.
  1. Land as habitat:
    • Many insects are adapted to build mounds on land.
    • These mounds are made using mud or soil, water and the saliva secreted by the insects.

    Example : Ants and termites.

  2. Water as a habitat:
    • Some insects live in water during the early stage of their life cycle.

    Example : Mosquitoes and dragonflies.

  3. Tree as a habitat:
    • Some insects can drill through the tree trunk and make a shelter for survival.
    • Leaves of trees are bent and folded by some insects to make a nest-like structure.

    Example : Bark beetles and weaver ants.

  4. Hives as a habitat:
    • Some animals live in groups. A group of insects is called a colony.
    • Animals make unique structures called hives, where many insects live together.
    • These hives are made using mud or wax. Hives are used both for storing food and laying eggs.
    • Hive-like structures made by wasps are called paper nests.

    Example : Honeybees and wasps.


Lifecycle of insects:

  • The life cycle of an insect can be divided into three or four stages.
  • Moulting and metamorphosis are prominent phenomena in the lifecycle of an insect.

Let us discuss the life cycle of an insect in brief.

  1. Egg stage: Insects lay a large number of eggs at a time. These eggs take some time to hatch or mature, which varies from insect to insect.
  2. Larval stage: Once the eggs are matured, hatchlings come out of them and start feeding. This stage is called the larval stage.
    • The larvae of different insects are known by different names.
    • Example : The larva of a silkworm and cockroach is called caterpillar and nymph, respectively.

    • The larva shed their skin multiple times by the phenomenon of moulting to grow into a pupa.
    • The phenomenon of growing into a pupa and then into an adult is called metamorphosis.
  3. Pupa stage: It is called the dormant stage. The pupa covers itself in a covering made of its own saliva and keeps growing.
    • The structure in which the pupa grows is called a cocoon.
    • On maturation, the adult insects come out of the cocoon.

Lifecycle of ants:

  • Ants live in colonies. Their colonies comprise male and female worker ants and a queen ant.
  • Male worker ants are smaller in size, whereas female worker ants are larger.
  • Their main function is gathering food, repairing the mound, taking care of eggs/larvae, and protecting the colony from intruders.
  • The queen ant lays a large number of eggs at a time which hatch to form new ants.
  • Ant undergoes three stages of development like other insects, i.e., egg, larval, and pupa.

Useful insects:

  • The Dung beetles push the dung balls into the soil and help fertilise the soil and clean the surrounding.
  • We get honey and wax from the honeybees.
  • Honeybees, butterflies, moths, etc., visit different flowers and help in pollination.
  • Praying mantis feeds on grasshoppers, crickets and other harmful insects that destroy vegetation.
  • The ladybugs prey upon many plant-sucking pests.
  • The silk used to make garments is obtained from cocoons of silkworms.
  • Larvae of dragonflies control the population of mosquito larvae in water, and adult dragonflies feed on flying insects.

Harmful insects:

  • Insects like locusts damage hectares of agricultural farms in no time.
  • Tree borer beetles damage the trees by digging into its trunk.
  • Aphids suck the sap (juice) from the plants and reduce the crop yield.
  • Bed bugs and mosquitoes bite humans and suck blood, causing many diseases.
  • Wasps and hornets feed on useful insects such as honeybees.
  • Termites and carpenter ants damage the wood-based items.
  • Silverfish (an insect), cockroaches, moths, etc., damage clothes made of silk and wool.

New Words:

Moulting: The shedding of the exoskeleton so that the insect can grow.

Metamorphosis: The process of changing of an immature form into an adult form through different stages.

Wax: A yellowish sticky substance made by honey bees.

Intruder: In this case, it means an enemy that can harm the insect.

Did You Know?

  • Some predatory beetles can dive deep into the water to hunt for food. There the diving beetles can enjoy all their food without any competition.
  • Ants can farm and raise other creatures like fungus, aphids and other insects to get benefits from them.
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