The insect life cycle involves various stages of development, depending on the type of metamorphosis an insect undergoes. There are generally three types of metamorphosis: simple, incomplete, and complete.
Types of Metamorphosis
Simple Metamorphosis
This is the simplest form, often seen in primitive wingless insects like silverfish.
The young insect hatches from an egg and looks similar to its adult form but smaller.
It grows by molting (shedding its exoskeleton) several times until it reaches adulthood.
No distinct larval or pupal stages exist; the young consumes the same food as adults.
Incomplete Metamorphosis
Insects undergo three life stages: egg, nymph, and adult.
Nymphs resemble miniature adults without wings; they molt several times as they grow.
Wings develop externally during these molts and are fully formed at the final molt into adulthood.
Examples include grasshoppers and dragonflies.
Complete Metamorphosis
This involves four distinct stages: egg, larva, pupa, and adult.
Larvae (e.g., caterpillars) look very different from adults and often eat different foods.
After several instars (larval stages), larvae transform into a pupa where internal reorganization occurs to form an adult body.
Examples include butterflies, moths, beetles, ants, bees, wasps.
Common Stages Across All Types
Egg: The initial stage where development begins after fertilization or parthenogenesis in some species.
Immature Stage: Depending on the type of metamorphosis:
Nymphs for incomplete metamorphosis,
Larvae for complete metamorphosis,
Young resembling adults for simple metamorphosis.
Adult: The final stage capable of reproduction; growth ceases once this stage is reached.
Insects must molt periodically due to their rigid exoskeletons that cannot expand with growth. Each molt allows them to increase in size until reaching adulthood when no further molting occurs.