Instar facts for kids

An instar is a special stage in the growth of an insect larva. Think of it like a growth spurt! During each instar, an insect larva eats a lot and gets bigger.

For example, a housefly larva goes through three instars. After eating and growing in one stage, it sheds its hard outer skin. This process is called moulting. Its outer skin is like a tough suit of armor called an exoskeleton. Once it sheds this old skin, it can grow even more before its new, larger exoskeleton hardens.

After the third instar, the housefly larva changes into a pupa. This is the next step in its development. Inside the pupa, the insect transforms. Finally, an adult housefly, also called an imago, comes out of the pupa. This is the familiar housefly we see flying around.

For many insects, the larvae do most of the eating and growing. The main job of the adult insects is to reproduce and lay eggs for the next generation.

Insect Growth Stages

Insects grow in different stages, and an instar is one of these important steps. It's the period between two molts. Imagine you're growing, and your clothes get too small. You need new, bigger clothes! Insects do something similar with their skin.

Why Insects Molt

Insects have a hard outer shell called an exoskeleton. This exoskeleton protects them, but it doesn't stretch or grow. So, for an insect to get bigger, it has to shed its old, tight exoskeleton. This shedding is called molting. After molting, the insect has a soft, new exoskeleton underneath that can expand before it hardens. This allows the insect to grow in size.

Different Instars

The number of instars can be different for various insects. Some insects might have only a few instars, like the housefly with three. Others, like some caterpillars, can have many more instars, sometimes five or six, as they grow from a tiny larva to a large one. Each instar is a time of active feeding and growth.

From Larva to Adult

After an insect larva completes all its instars, it usually changes into a new stage. For insects like butterflies and flies, this next stage is often a pupa. Inside the pupa, amazing changes happen as the insect transforms into its adult form. The adult insect then emerges, ready to reproduce and continue its life cycle.

Images for kids

• 

  Imperial moth (Eacles imperialis) development from egg to pupa, showing all the different instars

• 

  Two instars of a caterpillar of Papilio polytes

See also

In Spanish: Estadio (biología) para niños