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:

• Purchase a scoop of mealworms from a local pet store or try to get some from a friend who already has a culture
• Fill a large glass jar with bran (a cereal grain available in grocery stores) or whole wheat flour or corn meal
• 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)
• Pour in the mealworms

The mealworms will begin to burrow into the bran or flour and will start to 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.

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.

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.