UCMP Lessons  

Mealworm Metamorphosis

Author: Jolene Routson

Overview: Students will observe offspring (mealworms) that do not initially resemble their parent organism (darkling beetles) throughout complete metamorphosis. Students will also create and maintain an appropriate habitat for the mealworms.

Lesson Concepts:

Grade Span: 3–5


Advance Preparation:

— Mealworms may be purchased in advance and placed in a refrigerator.
— Basic discussion regarding inherited traits is suggested.

Time: 50–60 minutes for initial observation and set up. Approximately 10–15 for daily observations.

Grouping: Solo or pairs

Teacher Background:

Mealworms are raised commercially as food for many reptiles, amphibians, rodents, birds, and other small animals. The mealworm is actually an insect that undergoes complete metamorphosis. It is not a worm at all. Mealworms are the larvae of “darkling” beetles. They have four life stages: egg, larva, pupa, adult. Students will be introduced to the mealworm during the larval stage. The larvae are very lethargic and move clumsily. The exoskeletons will be shed (or molted) about five to seven times as they grow.

Under ideal conditions, the larval period lasts about eight to ten weeks. However, it can last several weeks longer at lower temperatures or due to lower food availability. When the larva molts for the last time, a soft new exoskeleton in the shape of a pupa will emerge. The change from larva to pupa is the mealworm’s first metamorphosis. The pupae move very little and do not eat.

Approximately two to three weeks after pupation, an adult beetle will emerge from the exoskeleton. The adults are whitish after metamorphosis, but soon turn dark brown. Although they do not usually fly, they do crawl almost constantly.

Note: It is not necessary to include water; the mealworm will extract moisture from the fruit. Too much moisture will cause the bran to mold and the mealworms will die. Add a new piece of fleshy fruit or vegetable once a week.

Teacher Resources: Fabulous animal/insect life cycle printouts and quizzes are available through Enchanted Learning at www.enchantedlearning.com/coloring/lifecycles.shtml.

Explore these links for additional information on the topics covered in this lesson:

Teaching Tips:

— The key point in this lesson should be that although the mealworm larva initially looked nothing like its parent, it matured to look similar to the parent because of inherited traits. However, unless you have an ongoing mealworm culture, students will not see the parent generation and will have to infer their appearance by looking at the adult forms that result from their mealworms.
— Do not create habitats using Styrofoam or cardboard containers because the mealworms can chew through these materials.
— Mealworms are available at both pet stores and bait shops. However, if possible obtain worms from a bait shop because they are less likely to be fed hormones that can stop their metamorphosis into beetles.

Vocabulary: metamorphosis, egg, larva, pupa, adult, inherited, traits, exoskeleton


  1. Allow students to view a mealworm larva on a sheet of paper. Ask students to guess what they think this larva will look like as an adult. What will it become?
  2. Provide students time to observe the mealworm and record at least three observations. Tell them to include a sketch of the larva at this stage.
  3. Inform students that they will be creating personal habitats for the mealworms and observing their changes through the next several weeks.
  4. Each student (or pair of students) should fill a plastic container with approximately 3 cm of wheat bran. Note: small yogurt containers work well for individual habitats.
  5. Place two mealworms into each container.
  6. Add a piece of potato or apple to the container for moisture. Label each container with the student’s name.
  7. Place the lid loosely on the container (or poke small holes in it) and place in a dark area.
  8. Three times a week observations and sketches can be recorded in an observation log. Teachers may choose to do observations three times a week rather than daily due to the number of weeks involved in the complete metamorphosis.
  9. Upon completion of the metamorphosis, ask students to draw the life cycle of the darkling beetle and answer the following questions from their data: What are the stages of mealworm development? What other animals go through metamorphosis? Why do you think the mealworm sheds its skin? How many times did the mealworm shed? Did both of your mealworms mature at the same rate? What other animals do not initially resemble their parents, but mature to look similar?


The possibilities for continued experiments are endless. However, some ideas for charts or tables that may be developed are:

Further observations and comparisons can be made by observing other insects’ life cycles. Possible insects include: crickets, grasshoppers, stick insects, fruit flies, and mosquitoes.

Updated November 19, 2003

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