Why some insects are attracted to Lights?

At night, porch lights and other artificial light sources are usually buzzing with flying insects. Why are insects attracted to lights, and why do they keep circling around and around like that?

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Night flying insects evolved to navigate by the light of the moon. By keeping the moon's reflected light at a constant angle, the insects can maintain a steady flight path and a straight course.
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.

Nearly all insects are attracted to some form of light. Itís called phototaxis

ďSome insects, like cockroaches, are negatively phototactic and they will scurry away when the light comes on;mosquitoes are attracted to light in a certain spectrum.

Insects like UV light, but donít pick up on yellow or red lights. So, a lot of people put yellow lights on their front porch to keep bugs away.

Another interesting question is: Why do moths stay at lights? A moth's eyes, like a human's eyes, contain light sensors and adjust according to the amount of light the sensors detect. In high illumination, light from each of the moth's thousands of fixed-focus lens facets is channeled to its own sensor (ommatidium).

In low illumination, light from multiple lenses is channeled to the same ommatidium to increase light sensitivity. You probably experience a few moments of blindness when you turn on a bright light after your eyes have adjusted to darkness, or when you are suddenly in darkness after being in bright light. A moth's dark-adapting mechanism responds much more slowly than its light-adapting mechanism. Once the moth comes close to a bright light, it might have a hard time leaving the light since going back into the dark renders it blind for so long. In the case that the moth escapes, it won't remember the problem with flying too near the light and will probably find itself in the same predicament all over again.

Another possible explanation for why moths stay at lights is that they are mostly night-flying creatures and eventually respond to the light as they would to the sun -- by settling in for their daytime "sleep."