The Types and Stages of Insect Metamorphosis

A Series of Transformation From Egg to Adulthood

Black Swallowtail (Papilio Polyxenes) caterpillar pupating into chrysalis, Hill Country, Texas, USA
Danita Delimont / Getty Images

With a few odd exceptions, all insect life begins in the form of an egg. After leaving its egg, an insect must grow and undergo a series of physical transformations until reaching adulthood. (Only adult insects can mate and reproduce.) The transformative changes an insect passes through as it moves from one stage of its life cycle to the next is called metamorphosis. While about 10 percent of insects undergo what's known as "incomplete metamorphosis," the majority of insect species experience some dramatic changes as they mature.

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What Are the Types of Metamorphosis?

The physical transformation of insects from one life stage to the next is called metamorphosis. Insects may undergo gradual metamorphosis, complete metamorphosis, or none at all.

ThoughCo/ Debbie Hadley

Insects may undergo gradual metamorphosis, in which the transformation is subtle, or they can undergo a complete metamorphosis, in which each stage of the life cycle has a distinctly different appearance from the one before and the one after the current stage—or they can experience something in between. Entomologists classify insects into three groups based on the type of metamorphosis they undergo: ametabolous, hemimetabolous, and holometabolous.

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Ametabolous: Little or No Metamorphosis

The springtail is anametabolous, with no metamorphosis.

ThoughCo/ Debbie Hadley

The most primitive insects, such as springtails, silverfish, and firebrats, undergo little or no true metamorphosis over the course of their life cycles. Entomologists refer to these insects as "ametabolous," from the Greek for "having no metamorphosis." When they emerge from the egg, immature ametabolous insects look like tiny versions of their adult counterparts. They continue molting and growing until they reach sexual maturity. 

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Hemimetabolous: Simple or Gradual Metamorphosis

The periodical cicada is hemimetabolous, an insect with gradual metamorphosis.

ThoughCo/ Debbie Hadley

Gradual metamorphosis is marked by three life stages: egg, nymph, and adult. Entomologists refer to insects that undergo gradual metamorphosis as "hemimetabolous," from "hemi," meaning "part," and may classify this type of transformation as incomplete metamorphosis. 

Growth for hemimetabolous insects occurs during the nymph stage. Nymphs resemble the adults in most ways, particularly in appearance, exhibit similar behaviors, and typically share the same habitat and food as the adults. In winged insects, nymphs develop external wings as they molt and grow. Functional, fully-formed wings mark their emergence into the adult stage of the life cycle.

Some hemimetabolous insects include grasshoppers, mantids, cockroaches, termites, dragonflies, and all true bugs.

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Holometabolous: Complete Metamorphosis

The house fly is holometabolous, with complete metamorphosis.

ThoughCo/ Debbie Hadley

Most insects undergo complete metamorphosis over the course of a lifetime. Each stage of the life cycle—egg, larva, pupa, and adult—is marked by a distinctly different appearance. Entomologists call insects that undergo complete metamorphosis "holometabolous," from "holo," meaning "total." The larvae of holometabolous insects bear no resemblance to their adult counterparts. Their habitats and food sources may be entirely different from the adults as well.

Larvae grow and molt, usually multiple times. Some insect orders have unique names for their larval forms: butterfly and moth larvae are caterpillars; fly larvae are maggots, and beetle larvae are grubs. When the larva molts for the final time, it transforms into a pupa.

The pupal stage is usually considered a resting phase, although many active changes are occurring internally, hidden from view. The larval tissues and organs break down entirely, then reorganize into the adult form. After the reorganization is complete, the pupa molts to reveal a mature adult with functional wings.

Most of the world's insect species—including butterflies, moths, true flies, ants, bees, and beetles—are holometabolous.