Egg
All insects begin as an egg in the embryo stage. This is where simple development occurs, not unlike most animals including humans. In the egg, the insect develops early body functions, organs and features. This is a resting period of the insect life cycle. Development is occurring, but the embryo is not doing anything besides growing during the egg stage. Once the insect is ready to be born, it will emerge from the egg.
Larva
After hatching from the egg, the insect is in the larva stage. This stage is all about eating and growth. The larva exoskeleton is rigid; as the larva grows, this exoskeleton is shed, or molted, several times. Larva do not look like their adult incarnations. Caterpillars, grubs and maggots are all examples of insects in the larval stage. Their adult forms are butterflies, beetles and flies.
Pupa
After the larva stage is over, the larva forms a pupa, which acts as a covering. The pupa stage is where the insect transformation happens. Inside the pupa, the larvae is growing, developing new organs and muscles. New body parts, such as wings, are developing in the pupa stage. The larva maturation process is occurring, and it is changing into the adult form of itself.
Adult
The pupa stage ends when the insect transformation is complete. The insect sheds the pupa and emerges as the adult version of itself. The adult insect is now identifiable as an insect and has the three sections of its body, six legs, two antennae and, in most cases, wings. The adult phase of an insect life cycle is also where reproduction happens. Once metamorphosis is complete, the adult insect will reproduce ,and the metamorphosis will begin again with new life.