Life Cycle of a Moth: The 4 Stages explained

Like other insects that undergo complete metamorphosis, the life cycle of a moth has four main stages: egg, larva, pupa, and adulthood.

Briefly on each stage

Egg Stagetypically lasts about one week, the eggs are the size of 0.02 inches (0.5 mm)
Larva Stagecaterpillar stage lasts about one to 1.5 months, eventually the larva will become about half an inch to 2.5 inches long
Pupa Stagepupa stage lasts about a week or 2, depending on the species
Adult Mothadult moths live for 2 to 4 weeks, their size depends on the species

Stage 1 – Eggs

Moth eggs
Moth eggs

This is the first stage of a moth’s life cycle and typically lasts about one week. Just like other insects that undergo complete metamorphosis, the female moth lays her eggs on leaves and certain materials.

This hides them from possible predators, such as:

  • Wasps
  • Spiders
  • Birds
  • Shrews
  • Beetles

Common plants that moths lay eggs on are:

  • Ironweed (Vernonia)
  • Pussytoes (Antennaria)
  • Sacred datura (Datura wrightii)
  • Asters (Asteraceae)
  • Canada wild rye (Elymus canadensis)
  • Red twig dogwood (Cornus sericea)
  • Highbush cranberry (Viburnum trilobum)

Locating the moth egg is quite difficult, as it is usually translucent and microscopic, measuring only 0.02 inches (0.5 mm). They are usually laid in clusters or lines, depending on the position of the leaves and materials.

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On average, a moth can lay more than 150 eggs in about 3 weeks. These eggs will then hatch within 4 to 10 days, after which the caterpillars will emerge from their shells.

Stage 2 – Larva

Example of moth caterpillar
Example of moth caterpillar

As soon as larvae emerge from their shells, they will begin eating to trigger their fast-paced growth and development. They feed on the host plants (when outside) and the following materials (when inside):

  • Felt
  • Leather
  • Fur
  • Wool
  • Silk

During this stage, caterpillars will eat these materials as they contain a type of fibrous protein essential for their development.

Unfortunately, your clothes may be the first thing caterpillars will munch on, so you may find holes in things you left in your closet for a prolonged period of time. This is why it is crucial to recognize pest moths and keep them outside of your home.

It takes a moth larva about one to 1.5 months to reach its peak growth. It will measure about half an inch long (some can reach about 2.5 inches).

Then the larva will undergo the next stage, where it needs to find a safe space (such as cracks between boulders, firewood piles, and crevices between tree barks). In preparation for this stage, it transforms into an immobile and irregularly-shaped solid structure (usually known as a cocoon or chrysalis).

Stage 3 – Pupa

Moth pupa
Moth pupa

The pupal stage is when the moth larvae are dormant and focus most of their energy on developing their new body parts. 

Their immobility makes them even more attractive to predators. Some that are looking to feed on moth pupas are:

  • Ants
  • Hornets
  • Beetles
  • Spiders

As soon as the larva completes this development phase, it will slowly emerge from the hard shell where it’s hiding. This will then trigger the next stage of its growth.

Stage 4 – Adult Moth

Adult moth
Adult moth

As soon as the newly born moth comes out of its shell, it will take time to dry its newly-developed wings. This phase takes about 30 minutes.

Adult moths will live for about 2 to 4 weeks. Because of their relatively short lifespan, they usually begin mating somewhere between day 10 to 14.

They protect themselves with toxins during reproduction because it takes about 9 hours to complete the process. The male moths’ toxins prevent the predators from getting near them while they are in contact with the female.

What is Complete Metamorphosis?

Complete metamorphosis refers to a biological process where an insect/animal goes through stages where it completely alters its physical appearance. Insects that undergo this type of transformation usually develop wings during their adult stage.

Insects that undergo complete metamorphosis have to undergo all 4 stages. In contrast, those that go through incomplete metamorphosis pass through 3 stages — egg, nymph, and adulthood.

Some of the species that undergo complete metamorphosis are:

  • Butterflies
  • Flies
  • Bees
  • Beetles

mentioned above. This contrasts with those that go through incomplete metamorphosis and only have three main stages–egg, nymph, and adulthood.

Some other species that undergo complete metamorphosis include the following:

  • Butterflies
  • Flies
  • Bees
  • Beetles

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