Do Mealworms Prefer Light or Dark? Experiment

• Joseph, Jesse, and Hannah

Introduction:

Mealworms, scientifically known as Tenebrio molitor, are the brown and white colored worm-like larvae of the darkling beetles. They go through a life cycle of transforming from larvae into pupa and then finally into adult darkling beetles. Mealworms are typically found near their food sources (both organic and rotting vegetation), underneath rocks (they highly prefer the dark), and in damp but warm places. Due to the darkness of their natural habitat, we have decided to examine the behavior of Mealworms when light conditions are changed. (Due to the similiarity and availability of Superworms, Superworms were used instead of Mealworms)

Hypothesis:

If Mealworms usually live under rocks and other environmental structures, then when a group of four Mealworms are placed in each side of a two-sided choice chambers with the number of bugs on each side being counted every 30 seconds for a total of 5 minutes under differing conditions like both sides being uncovered, one side being covered by a see-through material such as tissue paper, and one side being covered by an opaque material such as black construction paper, the number of Mealworms on the treated side will be the greatest for the trial with the opaque material due to the innate behavior of Mealworms liking the darker areas.

Problem Statement: Do mealworms have an innate preference for darker areas?

Materials:

• CFL bulb
• Lamp
• 8 Mealworms
• Tissue paper (dark green)
• Black Colored Construction Paper (opaque material)
• Two-sided choice chamber
• Stopwatch (iPhone)

Procedure:

1. Gather materials, set up lamp.
2. Place four of the Mealworms on one side of the chamber and four on the other .
3. Place the chamber underneath the light (or to the side as to not fry the worms if a CFL is not available). Start the stopwatch and count and record the number of Mealworms on each side every 30 seconds for a total of 5 minutes.
4. Repeat steps 2-3 covering one side of the chamber with dark green-colored tissue paper.
5. Repeat steps 2-3 covering one side of the chamber with the black construction paper (opaque material).
6. Repeat steps 3-5 as many times as time permits
7. Calculate the averages across trials in the number of Mealworms on each side.
8. Analyze the results with the use of graphs and chi-square analysis.

Variables:

• Control
  • During experimentation and across trials:
    • Lamp placement stayed the same
    • Bulb stayed the same
    • Position of the choice chamber under the lamp stayed the same
    • Angle of lamp stayed the same
    • Mealworms used stayed the same
    • Choice chamber orientation (left-right) stayed the same
    • Temperature stayed the same
    • Placement of the covers stayed the same
    • Ambient light stayed the same
    • Number of Mealworms on each side stayed the same
    • Time spent recording data stayed the same
    • Interval of data collection stayed the same
• Independent Variable: Different covers (no cover, tissue paper cover, construction paper cover)
• Dependent Variable: Final amount of Mealworms on each side

Data and Graphs:

Control

Average # of Mealworms for No Cover (left)- 3.5

Average # of Mealworms for No Cover (right)- 4.5

Tissue paper

Average # of Mealworms for No Cover- 2

Average # of Mealworms for Covered- 6

Black Construction Paper

Average # of Mealworms for No Cover- 1

Average # of Mealworms for Covered- 7

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Data Analysis:

Control:

Null Hypothesis: If 8 Mealworms are allowed to move freely between two-choice chambers with both sides having similar amounts of light, then 50% of the Mealworms (4 Mealworms) will end up being on each side after 5 minutes.

Average for left side = 3.5 Mealworms

Average for right side = 4.5 Mealworms

=

df = n-1 = 2-1=1

Since the p-value is between .5 and .75 and not less than .05, we accept the null hypothesis. Thus, the data is not statistically significant and the variation in the data was due to random chance.

Tissue Paper:

Null Hypothesis: If 8 Mealworms are allowed to move freely between two-choice chambers with one side being covered with dark-green tissue paper, then 50% of the Mealworms (4 Mealworms) will end up being on each side after 5 minutes.

Average for uncovered side = 2 Mealworms

Average for covered side = 6 Mealworms

=

df =n-1 = 2-1= 1

Since the p-value is between .1 and .25 and not less than .05, we accept the null hypothesis. Thus, the data is not statistically significant and the variation in the data was due to random chance.

Black Construction Paper:

Null Hypothesis: If 8 Mealworms are allowed to move freely between two-choice chambers with one side being covered with black construction paper, then 50% of the Mealworms (4 Mealworms) will end up being on each side after 5 minutes.

Average for uncovered side = 1 Mealworms

Average for covered side = 7 Mealworms

=

df =n-1 = 2-1= 1

Since the p-value is between .01 and .05 and less than .05, we reject the null hypothesis. Thus, the data is statistically significant and the variation in the data was not due to random chance and thus can be attributed to the variable of the black construction paper.

Results:

The experiments resulted in an approximately even distribution for the control (3.5 and 4.5 Mealworms on each side) and distributions skewed towards the covered sides for the trials with tissue paper cover (6 Mealworms on average on the covered side) and construction paper cover (7 Mealworms on average on the covered side). Across the different trials, Mealworms only exhibited sporadic movement during the control trials which can be seen in the sporadic trend of the line graph. When there was a cover, the Mealworms trended towards the covered side as evident in the line graphs of the movement.

Conclusion:

Based on the results, it can be seen that the Mealworms prefer darker areas. This can be seen in the trends evident in the line graphs across the trials as well as in the end results. The sporadic movement present in the control showed us that without any difference in light, the Mealworms did not have an evident preference for a side. This is contrasted with the trends towards the covered sides evident in the tissue paper and construction paper trials. However, the chi-square analysis for the tissue paper trials showed that the data was not statistically significant. Thus, we cannot conclude anything about how a lesser degree of darkness (such as the one induced by the tissue paper) affects Mealworm behavior. We can only conclude that a greater degree of darkness (such as the one induced by the construction paper) affects behavior based on chi-squared analysis. Overall, it is evident that Mealworms demonstrate an innate preference for darker areas with increasing preference for increasing degrees of darkness, substantiating our hypothesis.

References

Darkling Beetles (Tenebrio). (2009, July 31). Retrieved April 6, 2015, from http://lhsfoss.org/fossweb/teachers/materials/plantanimal/tenebriobeetles.html

Iowa Insect Information Notes. (2005, July 14). Retrieved April 6, 2015, from http://www.ipm.iastate.edu/ipm/iiin/mealworm.html

Mealworms. (2015, January 1). Retrieved April 6, 2015, from http://mealwormcare.org/