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Insects - Mealworms

Insects - Mealworms Mealworms are popular classroom observational insects. They are easy to obtain, and they undergo complete metamorphosis. The 4 stages of complete metamorphosis are egg, larva, pupa, and adult.

Mealworms are the larval stage of darkling or flour beetles. They can be purchased very inexpensively from most pet stores where they are sold as food for fish, turtles, frogs, toads, lizards, and birds.

It's easy to observe how mealworms grow and change form. Here's how:

  1. Purchase a scoop of mealworms from a local pet store
  2. Fill a large glass jar with bran (a cereal grain available in grocery stores) or whole wheat flour or corn meal
  3. Add a slice of apple, potato, or other moist fruit or vegetable to the jar for moisture (remove and replace it if it gets moldy or dries out)
  4. Pour in the mealworms

This is what should happen:

  1. The mealworms will begin to burrow into the bran or flour
  2. The mealworms will grow. As they grow, they will shed their exoskeleton (hard outer covering). You will be able to see these used exoskeletons on the surface of the bran. You can even pour some of the bran from the jar onto a piece of paper and gently sort through it to see that the mealworms have grown and to find more of their shed exoskeletons. Each mealworm will shed its exoskeleton from 9 to 20- times depending upon environmental conditions such as temperature and moisture. They will stay in this larval stage for about 10 weeks.
  3. The larva will turn into pupa more quickly if it is warm; it may take longer if temperatures are cooler. Mealworms can even overwinter in their larval form if it is very cold. The pupa of the beetle is a small and firm. It does not move or eat. Inside it, the larva is slowly changing form into an adult beetle.
  4. In 2-3 weeks, the skin of the pupa will split open and the adult beetle will emerge. At first, the beetle will be lighter in color and soft. Within a few hours, its skin will darken and its exoskelton will harden.

With enough room, you can keep the adults beetles which will mate and produce eggs. The eggs will hatch into mealworms (larvae) in about 2 weeks, and the cycle will continue.

For more information about metamorphosis, visit Insects - Metamorphosis.

Visit the following websites to find out more information about mealworms as well as suggestions for classroom activities.

Keeping and Raising Mealworms

Look at the information for Regular Mealworms - Tenibrio molitor.

  1. How many eggs do adult female beetles lay?
  2. What do the eggs look like?
  3. Why are the eggs hard to see?
  4. After the eggs hatch, why is it hard to see the the larvae?
  5. What color are the adult beetles?

 

How To Culture Mealworms

Mealworms, of course, are not worms at all. They are larvae. Even as larvae, they still have all the basic parts that all insects have: 6 legs, 3 body parts, and 2 antennae. The first segments of their wormlike body are the head, the middle segments are the thorax, and the end segments are the abdomen.

  1. About how long do the adult beetles of mealworms live?
  2. About how many mealworms can your culture in a wide-mouthed gallon jar?
  3. What is frass? If you are serious about growing LOTS of mealworms, what should you do with the frass?

 

Ohio State University Extension Factsheet

Like all insects, mealworms breathe through special holes called spiracles that are located on the sides of their bodies.

  1. In your home, if you have mealworms as pests rather than as pets, what kinds of human food might you find them in?

 

Mealworms

Sometimes people who like to fish use mealworms as bait.

  1. Even though mealworms can be considered to be pests, are they a serious problem in homes?

 

Mealworm Locomotion

Do the mealworms slither like a worm or use their tiny legs (6 of them) to move?

  1. This experiment helps students discover how different surfaces affect the distance mealworms travel in 2 minutes. If you are raising mealworms, duplicate the experiment in your classroom. Record your data on a graph. The part about the nail polish seems worrisome, but no mention is made about whether or not this harms the mealworms. Record whether the nail polish has any effect on your larvae.

 

Troubled Times : Mealworms

Yum.

  1. Some people actually eat insects. What does this individual say that fried mealworms taste like?

 

Teacher Resources

Mealworms
A classroom teacher describes how she has kept a colony of mealworms going for 20 years. She has suggestions for classroom activities such as putting an indivdual mealworm in a plastic cup for each student to raise to maturity and ideas for recording student data.

Rearing Mealworms
More information about the care and feeding of mealworms.

A good book about mealworms is:
Adrienne, Mason. Mealworms. Kids Can Press: New York, 1998.
It describes doing an experiment about the kinds of food that mealworms prefer. It suggests putting various foodstuffs around the outside of a paper plate such as grass, peanut butter, flour, paper shreds, etc. and then putting a few mealworms in the middle of the plate. Observe which foods the mealworms wiggle to.

Places to order mealworms and other creepy, crawlies:

Image is copyrighted by ArtToday. Used by permission. All rights reserved.

Author: LINDA MOSBACKER - Email linda.mosbacker@slc.k12.ut.us