Why bugs are attracted to lights?

Many insects are attracted to light, and some fly right into the light itself. Moths commonly hover around lights and are active at night. This attraction to light is a response called phototaxis.

When insects fly at night they use light sources such as the moon for navigation. Light from a distant source reaches both eyes with the same intensity. This enables the insect to fly in a straight line with both wings beating at the same rate.

If the light is from a closer source such as a candle or lantern, it changes the insect's perception. The light is perceived stronger in one eye than in the other eye. This causes the wing on one side to move faster. The insect then approaches the light in a spiral path, eventually drawing it into the light itself.

One good way to know if an insect is nocturnal is to look at their antennae. Insects with poor eyesight have longer antennae. Many varieties of beetles have poor eyesight. They use their antennae to move around safely at night.

Source: http://www.suite101.com/article.cfm/science_for_kids/11252