Like a Moth to a Flame by Yunpeng (bob) Li

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Generally, the position of the sun is first located in the brain of insects; this signal is then integrated with the circadian clock to obtain an unambiguous compass direction for migration. On clear days when the sun itself is visible, information about solar elevation as well as azimuth is collected by both eyes and processed in the central complex of the central brain, which is likely the site of sun compass. On cloudy days when the sun cannot be seen, insects utilize polarized skylight and electric field vectors to help locate the sun. The compound eyes of insects are able to sense the electric field vectors of linearly polarized light, which is arranged in concentric circles around the sun and indicate the position of the sun. These skylight cues, integrated with the internal circadian clock, help constantly adjust to maintain the same flight direction in different weather conditions.

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As a variety of cues are available to insects at a time, they are used in a hierarchical way. In other words, an insect would always prefer a specific source of cue to another. Different insects have different preferences of cues. For those who migrate nocturnally, moon orientation is likely to be the most favored mechanism, stellar orientation the second. Over thousands of years of existence, selection has favored different navigation mechanisms in different insect species, which is related to their distinct behaviors. Although some detailed mechanisms of orientation are still unknown, more knowledge would be obtained in the future, and because of human influences, those mechanisms might also change gradually over time to keep insects the fittest to their environment.

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References

Heinze, S., & Reppert, S. M. (2011). Sun Compass Integration of Skylight Cues in Migratory Monarch Butterflies. Neuron , 345-358.

Sotthibandhu, S., & Baker, R. R. (1979). Celestial Orientation by the Large Yellow Underwing Moth, Noctua pronuba L. Animal Behavior , 786-800.

Wolchover, N. (2011, 3 25). Live Science. Retrieved 11 23, 2016, from Why Are Moths Drawn to Artificial Lights?: http://www.livescience.com/33156-moths-drawn-artificial-lights.html