Why do moths and some flies fly towards light?

I have my window open and a light on inside. Outside it is dark, I was wondering why all the moths and daddy long-legs all fly towards the light.

Thanks x

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  • Ron971
    Lv 6
    1 decade ago
    Best Answer

    Flying insects use the sun or the brightest light source as a reference for navigation. The sun or moon work nicely since they are a great distance away making the light rays, for all practical purposes (like navigation), parallel to each other. The insect observes the angle of the point of light as it starts its journey and returns simply by flying the reciprocal or opposite angle for the same length of time.

    The problem for the insect comes when it uses a nearby source of light such as a light bulb as it navigates. The rays from a bulb are no longer strictly parallel since light is emitted from all points of a relatively large global surface of the bulb. As the insect tries to maintain a constant light-to-eye angle it has to make constant corrections by turning in flight. This results in a spiraling flightpath bringing it closer and closer to the bulb until they are, shall we say "overcome by the heat", or they run into the window glass.

  • Anonymous
    4 years ago

    This Site Might Help You.

    RE:

    Why do moths and some flies fly towards light?

    I have my window open and a light on inside. Outside it is dark, I was wondering why all the moths and daddy long-legs all fly towards the light.

    Thanks x

    Source(s): moths flies fly light: https://shortly.im/yp34w
  • 1 decade ago

    They use the moon and other light sources to navigate. Imagine the moon is over your left shoulder, and if you were flying in a straight line, you would always have the moon over your shoulder (well, close enough to be a straight line if it were a short flight). This works because the moon is far away, and your flying doesn't change its relative position by much at all.

    Now, if you instead use a nearby light for a direction standard, if you keep it in the same position off your shoulder, you will turn in a tight circle. This is, I understand, what happens to moths.

  • mom
    Lv 6
    1 decade ago

    Moths seem to use light only as a way of telling which direction is up. If you fly toward the moon, there's no danger of bumping into it, but you will succeed in flying up into the air instead of down into the ground.

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  • 1 decade ago

    I think its the way moths navigate around, they navigate by the moon especially when the moon is bright and when they see a different light source they get confused and just fly to the light source

  • Anonymous
    1 decade ago

    Moths are positively phototactic, meaning they automatically move toward light.

    Go to http://www.howstuffworks.com/question675.htm as this goes into lots of detail about it. Hope that helps.

  • 4 years ago

    I think they go toward light to find something to eat.

  • 1 decade ago

    Because they are " enlightened " ( get it lightened )

    its actually they think that the light source may be a beautiful meadow with flowers.

  • 1 decade ago

    Hi there.

    Current theory is, they steer by moonlight and the stronger light confuses them.

    cheers, Steve.

  • Anonymous
    1 decade ago

    they get turned on by the light.

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