Moths are attracted to light and this is because they use stars for navigation—specifically, the moon and the North Star.
Insects evolved before there were artificial lights.
Celestial objects such as the sun and the moon were their only sources of light.
Because moths can detect light with their eyes, they fly towards it in order to navigate.
Why Moths are Attracted to Light
To explain why moths are attracted to light, it is important to explain how moths navigate in the first place.
The fact that they use the moon for navigation might seem surprising at first because the moon does not provide a steady source of light: it appears and disappears as it moves across the sky.
Another point that might surprise you is the fact that moth eyes are not very good at detecting contrast.
Contrast allows us to see silhouettes, but this depth perception doesn’t appear to help moths navigate.
A Moth’s Eyes
Moths can detect sources of light because they have photoreceptors in their eyes called “rhabdoms.”
Rods and cones make up humans’ retinas.
These rods and cones allow us to see in dim light and detect contrast.
Rhabdom cells wholly make up a moth’s retina.
These make it possible to detect a source of light with the naked eye.
The nighttime navigation system using the moon seems odd when you think about how unreliable a compass based on celestial objects would be.
In fact, moths don’t use the moon to determine a course precisely.
Moths have compound eyes, which provide them with a very wide field of view.
They can see in all directions at once, and their field of vision contains the moon.
The fact that moths are attracted to light might be surprising, but it does make sense as an evolutionary trait.
Many moths fly at night, and they use the moon to navigate by.
Since artificial light also emits visible light that looks like the moon to a moth, they fly towards it because it provides them with navigation cues.
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