Investigation 2 – Mealworms!

Name: Avril, Emily (31,13)

Class: 110                    Date: 4/7/12

What is the subtle difference between ethologists and animal behaviorists?


–      the scientific study of animal behavior through observation only

–      no manipulation of animals’ environment (occurs in natural environment)

–      e.g. Jane Goodall

Animal behaviourist

–      involves manipulation of animals’ environment to study animal behavior

–      to a certain degree, occurs in artificial environment


Life cycle of mealworms



(from left to right) Mealworm (larva), pupa, adult beetle



Length of mealworm: 2.5cm
Number of segments: 10
Colour: Black head and light brown body

Other observable characteristics:


–      Body is long and thin, tapering off to a pointed tail

–      Body is made up of many dark brown bands that separate it into segments

–      Body is hard and has a rough texture

–      Length is roughly 2.5 cm; Width is roughly 0.3 cm

–      Has six legs and feelers

–      Legs are at the first 0.3 cm of body (thorax)

–      Resembles centipede


–      Moves forwards with abdomen (without legs) in contact with the ground, dragging behind it

–      The dark brown bands contract on either side of its body to help it curl up or change direction

–      Moults and leaves dead skins/shells that are brown in color, translucent and fragile

–      No noise made

–      Almost constantly eating


–      Why is it constantly eating?

–      Can it move backwards?

–      When touched on its back, what is its reaction?





1. Light


The aim of the experiment – to find out mealworms’ reaction to darkness and light



In darkness, the mealworms will be located throughout the black box. When exposed to light, the mealworms will be located in the darkest area of the black box.


Independent variable – variable to be changed

amount of light in the box


Controlled variables – to be kept constant

location of experiment, amount of food in the box, number and type of mealworms, temperature of box


Dependent Variable – results to be measured

locations of the mealworms in the box after 1 minute



–       the mealworms can sense light and darkness

–       the mealworms’ locations are only affected by the amount of light in the box


Materials and apparatus:

  • 5 mealworms
  • Pen light
  • Black box with a hole covered in plastic at the top and flaps at the bottom
  • Stopwatch





1. Place 3 mealworms in the middle of the box, between the hole and the flaps. Orientate them facing towards the hole.

2. Close the box and leave it in a dark place for 1 minute.

3. Open the box and observe the locations of the mealworms.

4. Gather the mealworms and place them in the same position as step 1.

5. Close the box and place it in the same dark place. Shine the pen light through the hole in the box for 1 minute.

6. Open the box and observe the locations of the mealworms.

7. Compare the mealworms’ locations in both setups.

8. Repeat steps 1-7 two more times, each time with different sets of mealworms.
Results (common observations between all 3 rounds of the experiment):

When in darkness for 1 minute When exposed to light for 1 minute
–       one crawled under the flaps-       the other 2 are leaning against sides of the box; crawling normally like in the bowl-       their locations are spread out evenly throughout the box –       All mealworms are located away from the bright spot of light in the box-       2 of them are underneath the flaps-       The other is crawling along the side of the box and leaning against the side

–       Their locations are concentrated underneath the flaps


Data Analysis – What you observed and give reasons to your observations.

  • They prefer darkness to light
  • The darkness may make them feel safer from predators, so they are more willing to expose themselves in the open
  • Similarly, light may signal predators, causing them to hide
  • Light is often accompanied by heat. The heat with the light may cause water to evaporate faster from their bodies, which will kill them. So they are not willing to expose themselves in light.



The data supports my hypothesis that in darkness, the mealworms will be located throughout the black box; and when exposed to light, the mealworms will be located in the darkest area of the black box.


To further improve the experiment:

Seal the black box fully

  • The black box was not fully sealed, so some light was able to enter the box. This compromised part 1 of the experiment where the mealworms were left in darkness and could have affected its outcome.

Replace the pen light with a light source that emits less heat

  • The penlight emitted a lot of heat. This could have affected the mealworms’ locations and the experiment only wants to test their reactions to light, not heat.


2. Touch


To find out how mealworms respond when touched with different objects



The mealworms will react violently when touched with the wooden stick, but will not react when touched with the paintbrush

Independent variable

The object used to touch the mealworm

Constant variables

The number and type of  mealworms, the other components of their environment (e.g. the amount of light and temperature)

Dependent variables

The reactions of the mealworms


  • 3 mealworms
  • a wooden stick with one end covered in cotton
  • a soft paintbrush


  1. Use the wooden end of the stick to brush one mealworm from head to tail
  2. Repeat step 1 with the other 2 mealworms
  3. Use the paintbrush to brush all 3 mealworms from head to tail
  4. Record your observations


When using soft brush to stroke from head to tail

First try:

  • they start writhing and contracting
  • one tilts its head backwards

Afterwards, they stopped writhing, but still contract slightly and stop moving forward.

One of them does not have any reaction at all (does not even stop)

2 out of 3 of them stopped contracting altogether after 3 tries; only stopped slightly while being stroked


When use rough wooden side of cotton bud to stroke from head to tail

  • head tilts backwards
  • tries to move forward; more wriggling and “struggling”
  • one of them writhes; another starts contracting slightly; the last one does not respond except by stopping
  • **same reactions for rest of tries


The results partly support my hypothesis that the mealworms will react violently when touched with the wooden stick, however they did react, just less violently than when touched with the wooden stick.

– the other experiment will be added at a later time –






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