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Larva: Definition & Types

Instructor: Julie Zundel

Julie has taught high school Zoology, Biology, Physical Science and Chem Tech. She has a Bachelor of Science in Biology and a Master of Education.

When your child looks nothing like you, you may have concerns. Or, you could just be an animal that has a larval stage. This lesson will define larva, look at different types of larva, and then go over some advantages of having this life stage.

What is Larva?

Did you know that maggots, or the larval stage of flies, can create a lot of heat when they gather together? In fact, the temperature can get so high (somewhere between 104 and 122 degrees Fahrenheit) that the maggots start to die off.

Fly larvae can get hot!
fly larvae

Oh, you knew that? Okay, how about this one? Caterpillars, or the larval stage of butterflies and moths, can eat upwards of 27,000 times their weight while in that life stage.

Wait, you knew that, too? Man, you are already a larva expert. Okay, okay. Let's try some more.

While the larval stage is short for some, it's quite long for others. For example, dragonflies can remain in their larval stage for years. They are also ravenous eaters and have been known to consume small fish!

A tadpole, or the larval stage of a frog, has gills like a fish. It isn't until the tadpole changes into a frog that it develops lungs.

Last one: Cnidarian, a classification that includes the jellyfish, also have a larval stage. You might not have seen them, but you may have felt them. Commonly referred to as sea lice, jellyfish larvae will sting people who unknowingly swim through them, resulting in a terrible, acne-like rash.

Oh come on! You didn't know that, did you?

So we know that insects (like butterflies and dragonflies,) frogs and Cnidarian (like jellyfish) have a larval stage, but what exactly is a larva (plural, larvae?) Such a good question.

A larva is an early stage in the development of an animal where it looks nothing like the adult. In order to become an adult, the larva must undergo metamorphosis, or a series of changes. Let's examine some of the animals that undergo metamorphosis and have a larval stage.

Insect Larvae

Most of the examples in our larva facts were insects, and that's no coincidence. Most insects (somewhere between 75 and 85%) have a larval stage. Let's check out what this looks like, so you can get an idea where larvae fit into the whole picture.

  • Egg: the insect lays an egg.
  • Larva: the egg hatches into a larva. The larva has an enormous appetite and grows.
  • Pupa: the larva makes itself a hard outer coating and becomes a pupa inside that coating. During this stage, the pupa undergoes metamorphosis.
  • Adult: the last stage is adult. Here the insect feeds and reproduces (eventually laying eggs.)

Butterfly life cycle
butterfly lifecycle

Wasps, ants, flies, butterflies, moths, beetles, fleas and scorpion flies are some examples of insects that have a larval stage.

Amphibian Larvae

Amphibians are a group of animals that includes salamanders, toads and frogs. While not all amphibians have a larval stage, many do. Let's check out what that looks like in frogs:

  • Eggs: eggs are released into the water in a jelly-like clump.
  • Larva: the eggs hatch and the tadpole emerges. The tadpole has gills and lives under the water.
  • Metamorphosis: eventually, the tadpole begins to change into a frog, growing legs, losing its tail, and developing lungs.
  • Adult: the tadpole becomes a frog, which will feed and reproduce (thus laying eggs and repeating the cycle.)

Frog life cycle from egg, to larva, to metamorphosis, to adult
frog lifecycle

Cnidarian Larvae

The Cnidarians are a huge group with over 10,000 species, including jellyfish, coral and sea anemones. Let's focus on the jellyfish life cycle to get a glimpse into the world of Cnidarian larva.

  • Eggs: jellyfish egg fertilization varies depending the species. Once the eggs hatch, they become larvae.
  • Larva: the larvae can swim on their own and are called planula. They are covered with cilia (hair-like structures) that help them swim. Eventually, the planula larvae fall to the bottom of the ocean and become polyps.
  • Polyp: the larvae affix themselves to a hard surface (like a reef) and become hard and stalk-like. The polyp continues to grow, even forming branch-like structures. The jellyfish can remain in this life stage for years.
  • Ephyra and Medusa: In this stage the polyp changes, forming baby jellyfish, which bud off from the stalk. The jellyfish are called ephyra at this stage. Eventually the ephyra grows into a full-sized jellyfish (called a medusa.)

Function of Larval Stage

We looked at the larval stages of three different types of animals: insects, frogs and jellyfish. You maybe wondering why some species go through larval stages at all. Let's check out the advantages:

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