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Build a Better Moth Trap: Will Different-colored Lights Affect How Many Moths You Catch?

Time Required Average (6-10 days)
Prerequisites You will need access to an area with moths. See the Experimental Procedure for details.
Material Availability Readily available
Cost Average ($50 - $100)
Safety No issues


You're coming into the house after a game of flashlight tag with your friends, but the front porch light isn't even on for you to see the door knob! What gives? Maybe your parents know that turning a light on means moths will gather there, and they don't want you letting them inside when you open the door. You've probably noticed how moths are attracted to lights at night. They will even fly dangerously close to flames in their journey toward light. In this animal behavior science fair project, you will learn a theory about why this is, and investigate whether moths are equally attracted to different-colored lights.


Determine if moths are equally attracted to different-colored lights.


David B. Whyte, PhD, Science Buddies

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Science Buddies Staff. "Build a Better Moth Trap: Will Different-colored Lights Affect How Many Moths You Catch?" Science Buddies. Science Buddies, 23 Oct. 2014. Web. 3 Oct. 2015 <http://www.sciencebuddies.org/science-fair-projects/project_ideas/Zoo_p059.shtml>

APA Style

Science Buddies Staff. (2014, October 23). Build a Better Moth Trap: Will Different-colored Lights Affect How Many Moths You Catch?. Retrieved October 3, 2015 from http://www.sciencebuddies.org/science-fair-projects/project_ideas/Zoo_p059.shtml

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Last edit date: 2014-10-23


Why do moths fly toward lights at night? This is a question that many people ask themselves at one time or another. Are they searching for something near the light? Or are they, perhaps, looking for a place to get warm? While there is no clear and definitive answer to this question, scientists generally agree that the answer has to do with the moth's use of the Moon to direct its flight, and its confusion when an alternative light source is present. When moths fly at night, they use light from the Moon for navigation. Light from the Moon comes from very far away, so the light reaches both of their eyes with the same brightness. Using this environmental cue from the Moon, the moth can fly in a straight line. If the light is from a closer source, however, such as a lightbulb or a campfire, it is perceived as stronger in one eye than in the other eye. This may cause the moth to turn in its flight path, rather than flying straight. Because it continues to turn as it flies, the moth approaches the light in a spiral path. At some point, the moth actually flies into the light source. Another question you might have is why do the moths tend to settle down near the light source? Some researchers have suggested that, having reached the bright light, the moth is tricked into thinking the Sun is out, and since it is nocturnal, it then settles in to sleep. In this animal behavior science fair project, you will set up light sources of various colors to determine if and how the color of the light affects the moth's behavior.

Terms and Concepts

  • Navigation
  • Environmental cue
  • Perception
  • Nocturnal
  • Control


  • Why don't insects fly toward light sources during the day?
  • Based on your research, what other kinds of environmental cues do insects and other animals use to help them navigate?
  • Can you think of reasons why it would be to the moth's advantage to fly toward a light source? Hint: See the HowStuffWorks, Inc. entry in the Bibliography, below, for some possibilities.


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Materials and Equipment

  • Small lamps (4); should hold standard screw-in lightbulbs
  • Colored lightbulbs, standard size; red (1), green (1), blue (1), and white (4); all available at most large hardware and department stores. Use the same wattage for each color of bulb.
  • Extension cord(s); to power lamps, if needed
  • Tape measure
  • Masking tape
  • Permanent marker
  • Flypaper; available at hardware stores and garden shops. You can use either the hanging kind or the flat paper kind.
    • As an alternative to using flypaper, you can set up a flash camera to take pictures of the lightbulbs and nearby moths, and count the number of moths in the picture. Be sure to include the masking tape labels you'll be making in the pictures. Also, keep track of which pictures are associated with each of your three trials.
  • Timer
  • Flashlight, so you can see as you make notes
  • Helper
  • Lab notebook
  • Graph paper

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Experimental Procedure

Important Notes Before You Begin:

You will need access to moths with which you can experiment. Doing this science fair project will depend on the seasons, since it involves studying moths around your house. Perform the following steps to make sure you will have enough moths to study.

  1. Locate outdoor lights near your home that are on at night, such as a porch light.
  2. Observe whether moths are flying around the light.
  3. Record your observations.
    1. Record the time, the location, and a rough guess about how many moths you observed.
    2. If there are a lot of moths (over 50 should be a reasonable cutoff, but use your own judgment), proceed with the rest of the experiment.

Setting Up Your Lights

In the steps below, you will set up your lamps and "moth catchers" (flypaper). First you will count the number of moths that are attracted to white light at each spot. With white lightbulbs in four of the lamps, you would expect to get similar numbers of moths at each light, right? But what if there is a stronger wind at one spot, or some other reason that the moths do not go to the white lightbulbs equally? The data with the white lightbulbs helps control for this kind of variation that is not due to the color of the lightbulb.

  1. Place the four lamps outdoors at night, as follows:
    1. Plug them each into a power source.
    2. Set up the lamps in an area that does not have other strong light sources.
    3. The lamps should be separated by at least 5 meters (15 feet). You can change the distance they are separated, if you choose, but avoid having one lamp too close to another lamp.
  2. Label the lamps 1–4, using the masking tape and the permanent marker.
  3. Make a note in your lab notebook about the location of each lamp. Also make a sketch, showing the position of each lamp.
  4. Remove the shades from the lamps. Any color in the shades could affect your results.
  5. Insert a white lightbulb into each lamp.
  6. Place a piece of flypaper near each lamp to catch the moths.
    1. If you have the hanging kind of flypaper, hang a piece of flypaper near each lamp.
    2. If you have the flat kind of flypaper, place it on the surface near the base of the lamp.
    3. The flypaper should be an equal distance from and the same orientation to each lamp.
    4. Measure the distance of the paper from each lamp and record it in your lab notebook.
    5. Make a sketch of how the paper is placed near each lamp.

Testing Your White Lightbulbs

The goal here is to catch enough moths that you can make meaningful comparisons between the different lamps, but not so many that it is difficult to count them. Between 20 and 80 moths might be a reasonable goal, but use your judgement to decide on the right number of moths.

  1. When it is dark, turn on the four lamps.
  2. Record the time at which the lamps were turned on.
  3. Watch the lights for 15 minutes. Use your timer.
  4. After 15 minutes, count the number of moths on each piece of flypaper.
  5. Record the number of moths in your lab notebook for each of the four lamps.
  6. Change the duration of the procedure, as needed, to catch a sufficient number of moths.
  7. Discard the flypaper with the moths on it.

Testing the Different-colored Lightbulbs

  1. Replace three of the white lightbulbs with the other three different-colored lightbulbs.
  2. Note in your lab notebook which of the original white lights have been replaced with colored lightbulbs.
    1. For example, #1: white, #2: red, #3: blue, and #4: green.
    2. Make a sketch of the positions of each colored lamp.
  3. Position the new flypaper, as you did in step 6 of Setting Up Your Lights.
  4. Turn the lamps on for 15 minutes. 15 minutes is just a suggestion. Feel free to alter the amount of time, as needed.
  5. After 15 minutes, count the number of moths on each piece of flypaper.
  6. Record the number of moths in your lab notebook.
  7. Repeat Testing Your White Lightbulbs and Testing the Different-colored Lightbulbs two more times. Having several sets of data ensures that your results are accurate and repeatable.
Note: Don't change the position of the colored lightbulbs for subsequent trials, since this would add another variable.

Analyzing Your Results

  1. Graph the data for each trial. Put the number of the light and the color of the lightbulb on the x-axis and the number of moths caught on the y-axis.
  2. Make side-by-side bar charts for all three trials and compare trends.
  3. Average the data by adding the data for each trial and dividing by three (the number of trials you performed). Graph the averages on another graph.
  4. What color appears to be the most "attractive"?

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  • As another control, place a fifth piece of flypaper near a light that is not turned on. What does this control tell you?
  • Repeat the procedure above, but put the lights in different locations. Does this change your results?
  • Test if heat is attracting the moths, rather than light. Use incandescent bulbs (they will be warm) and LED bulbs (very low heat output).
  • Try a black light to determine if moths respond to ultraviolet (UV) light.
  • Use the data from the trials with all white lightbulbs to correct for variation not due to color. For each light, divide the number of moths caught with the colored lightbulb by the number of moths caught with the white lightbulb. For example, if light #2 had 30 moths with the white lightbulb and light #2 had 15 moths with the red lightbulb, the ratio would be 15/30 = 0.5. Graph this ratio for each light.

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