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Wigglers: What are the Body Parts of a Meal-Worm?

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Author: Janice VanCleave

Problem

What are the body parts of a meal-worm?

Materials

  • 2 cups (500 ml) cornmeal
  • 4-cup (1-liter) or larger plastic container (such as empty margarine container)
  • slice of potato
  • small container of mealworms (available at pet stores)
  • paper towel
  • pencil
  • index card
  • desk lamp (optional)
  • magnifying lens
  • pencil
  • paper

Procedure

NOTE: At the end of this experiment, keep the remaining mealworms for the rest of the experiments in this chapter. You will need to plan what to do with the mealworms when you. are through experimenting. See page iv (dedication page), "Handling Insects and Spiders."

  1. Prepare housing for the mealworms.
    • Pour the cornmeal into the plastic container.
    • Place the potato slice and mealworms on the surface of the cornmeal.
    • Fold the paper towel in half twice and place it over the potato slice, mealworms, and cornmeal.
    • Secure the lid and make 10 to 15 airholes in the lid with the point of the pencil.
  2. Remove the lid and paper towel. Use the end of the index card to pick up one mealworm.
  3. Place the card on a flat surface under the lamp or near a window.
  4. Use the magnifying lens to examine the mealworm. Record your observations by drawing and labeling parts of the mealworm. Include head, antennae, legs, and body segments.
  5. Repeat steps 2 through 4, using 4 or more mealworms.
  6. When you are finished, return the mealworms and paper towel to the container. Secure the lid.

Wigglers

Results

The mealworm has a head and a wormlike, segmented body. The head has visible mouthparts and two short antennae. There are three pairs of legs attached to the body, one pair on each of the first three body segments after the head. The body is covered with a firm outer skin.

Why?

Mealworms do not have the same identifying features as adult insects (three main body parts and three pairs of legs). This is because mealworms are not adult insects. Mealworms are larvae, which are immature insects that differ greatly from the adult. Mealworms develop into adult insects called darkling beetles.

Mealworms have a well-developed head with mouthparts and short antennae. The first three segments behind the head are the thorax and the remaining segments are the abdomen. These two areas are more clearly separated in the adult stage. The mealworms have six legs, one pair attached to each thorax segment. They also have an exoskeleton.

Mealworms, like all larvae, grow through a series of molts as they develop. During molts, they shed their exoskeletons. The stages between molts are called instars. The last molt of the larval stage (active, feeding stage) results in the formation of a pupa, a non-feeding insect in the resting stage, or pupal stage. Next is the adult stage.

Let's Explore

Observe and compare the instars of the mealworms. Select 10 or more of the smallest mealworms and prepare a housing container as in the experiment. Measure the larvae and observe them with a magnifying lens every 1 to 2 days until the larvae pupate (form a pupa). This may take a few days to weeks, depending on how close your purchased larvae are to the pupal stage. (The pupae are inactive and look like pale mummies.) Science Fair Hint: Make diagrams of the instars and use the drawings as part of a project display. NOTE: Keep the pupae for other experiments.

Wigglers

Show Time!

  1. How do the bodies of the pupal and larval stages of the darkling beetle compare? Use the magnifying lens to study several pupae from the previous experiment.
  2.  
    1. Using a shoe box and a flashlight, test the response of mealworms to light. Cut a hole in one end of the lid of the shoe box. Make the hole slightly smaller than a flashlight's lens. Place 5 to 10 mealworms in the shoe box beneath the hole. Turn the flashlight on and stand it lens down over the hole. Leave the box undisturbed for 1 hour. Then remove the lid and observe the position of the mealworms.
    2. How do darkling beetle pupae respond to light? Repeat the previous experiment, using 5 or more pupae. Observe the pupae with a magnifying lens before and after placing them under the light. Look for any signs of motion.

Check It Out!

Some larvae have prolegs, which are fleshy legs attached to the abdominal region. Find out more about the body structures of larvae.

Wigglers

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