Although they look like it, the mealworm is actually not a worm. Instead, it is the larvae of a darkling beetle. The darkling beetle is a member of the phylum Arthropoda, meaning that it wears its skeleton on the outside of its body like a suit of armor. The mealworm transforms into this beetle after several weeks of going through the life cycle. Darkling beetles are also known as stinkbugs and are dark brown to black with hardened front wings that are not used in flight. Darkling beetles are about 1 inch long.
Darkling beetles go through a complete metamorphosis. This means they go through four distinct changes during their life cycle. The first stage is the egg stage. A female beetle lays an egg on a leaf and after a couple of weeks the egg hatches and the mealworm emerges. This is the larvae stage of the life cycle. The larva spends its time eating and growing. As it grows, it molts its soft shell periodically. This continues about a half a dozen times for about 3 months. The final molt reveals the next stage of the life cycle, which is the pupa stage. The shell around the larva has hardened and inside the mealworm is turning into a darkling beetle. The pupa does not eat or move. In approximately two weeks the beetle emerges from the pupa and the life cycle is complete.
Students can create a flip book to describe the four stages of the life cycle. To do this, they take a 9 by11 sheet of construction paper and fold it in half length-wise. They then fold it in half two more times to make three creases. Students cut along the creases to the fold, being careful not to cut the bottom paper. This creates four separate flaps. On the cover of each flap they write the name of each stage of the mealworm life cycle: egg, larva, pupa and adult. When the student lifts the flap they draw a picture of each stage on the top flap, and write a description of the stage on the bottom.
In order to show their understanding of the life cycle of a mealworm, students can create an informational poster showing each stage. Using different materials that can be found around the classroom or house, students can create each stage on the poster. For example, students can use a piece of rice as the egg stage and affix it to a real leaf. Students can use several pieces of rice or even a gummy worm to represent the mealworm! This activity allows students to demonstrate their creativity and knowledge of the life cycle and is a good culminating activity.
The best way to learn about the life cycle of a mealworm is to observe it. Teachers can help their students do this by ordering darkling beetle larvae from many companies across the country, such as Ward's Natural Science.
When the larvae arrive it is important to create a habitat that they will thrive in. Carefully read the instructions that arrive with the mealworms. Student should prepare their own observation journals in which to record their daily observations as the mealworm goes through the life cycle. Students can conduct investigations of how each organism responds to different stimuli, such as black and white surfaces, light, touch, barriers, moisture and temperature. These observations can be recorded in their observation journals. Over a two week period, students can observe the mealworms changing from the larvae to pupae. Being able to observe the darkling beetle emerge from the pupa is an experience they won't forget.