Insects are not very stable flyers, and try to keep the sun in the same spot in their view to fly in a certain direction. Since the sun is so far away, as they move, the sun seems to stay in the same place. If it moves, the insect alters its flight path to put the sun back in the same place in its view to maintain its course.

At night, there is no sun, and insects don't know the difference between the sun and lightbulbs. Since lightbulbs are so close, as the insects move and try to keep the light source in the same place in their view, they end up turning toward the light. They think they are flying in a straight line, but actually they are curving toward the light.

It is their natural navigation system that depends on the sun that is thrown off by lights that are closer than 93 million miles.

Artificial lights interfere with an insect's ability to detect the moonlight. They appear brighter, and radiate their light in multiple directions. Once an insect flies close enough to a light bulb, it attempts to navigate by way of the artificial light, rather than the moon.

Since the light bulb radiates light on all sides, the insect simply cannot keep the light source at a constant angle, as it does with the moon. It attempts to navigate a straight path, but ends up caught in an endless spiral dance around the bulb.

Some scientists believe light pollution is leading to a decline in certain insects. Fireflies, for example, have difficulty identifying the flashes of other fireflies where artificial lights are present.

Senior Education Officer, BNHS, India. www.bnhs.org

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