A Moth's Favorite Light

4.1 based on 14 ratings

Updated on Feb 13, 2014

Grade Level: 6th - 8th; Type: Physical Science, Life Science


The project is about determining whether moths are attracted to one color of light more than others.

The goal is to have the student review the literature about moths and light and then formulate and test a hypothesis about how moths respond to different colors of light.

  • Are moths attracted to one color of light more than to others?
  • Why are moths attracted to artificial light sources?

The reason why moths are attracted to artificial lights is not known. Part of the difficulty in answering this question may be due to there being many types of moths.

Some scientists have speculated that moths try to use artificial lights to navigate at night instead of moonlight. Light coming from the moon appears the same to both of the moth’s eyes, but the light from an artificial light source appears brighter in one eye than the other. In this scenario, the artificial light has a disorienting effect on the moth, causing it to spiral in toward the bulb.

Another idea is that the artificial light is mistaken by the moth for sunlight. When the moth gets close to the glowing bulb, it thinks it is in full daylight, and then settles down to sleep.

Still another idea is that moths use light from the moon to identify flowers whose nectar they feed on. According to this scenario, the light bulb might appear to be a source of food.

There are seven colors in the visible light spectrum. They are red, orange, yellow, green, blue, indigo, and violet.

Similar to an abstract

  • Color light bulbs (alternatively a rainbow fluorescent light)
  • Power strip
  • Light sockets/cords
  • Camera (optional)

Materials can be found on the Internet and are readily available.

  1. Read about the attraction of moths to artificial lights, and formulate a hypothesis that predicts whether moths will be attracted to some colors of light more than others.
  2. Place a white incandescent light bulb in a light fixture outdoors. Turn it on at night and watch for moths. Moths usually start to become active in late winter or spring.
  3. Wait for a warm, still night free of rain then set up an array of six colored lights. Choose colors that represent a range of the visible color spectrum. Space the lights about a foot apart. Turn off the white light.

As an alternative you can purchase a rainbow fluorescent light that projects all the colors of the visible spectrum.

  1. Stake a white translucent sheet about a foot above the lights. This will make it easier to see the moths from a distance.
  2. Set you alarm clock so you can observe moth activity around the colored lights several times during the night. Not all types of moths show peak activity at the same time of the evening.
  3. Observe and record the number of moths on the sheet each color in the light.

If you have a camera equipped for night photography, take a picture of the moths around the light to help you count them.

  1. Evaluate your hypothesis in view of your findings. If necessary revise it, and propose additional experiments to test the revision.


Number of moths

At 9:00 pm

At 12:00 am

At 3:00 am








Terms/Concepts: Moths; Artificial light; Moonlight; Feeding behavior (moths); Phototropism


Dr. Frost has been preparing curriculum materials for middle and high school students since 1995. After completing graduate work in materials science at the University of Virginia, he held a postdoctoral fellowship in chemistry at Stanford. He is the author of The Globalization of Trade, an introduction to the economics of globalization for young readers.

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