Why do insects like light?

You've probably observed that as you're getting set to curl up on your porch with a nice book, a swarm of insects begins to flutter above you, around the light bulbs or porch light! There is a reason why certain insects are drawn to different light sources while others are not. Because insects attracted to light, such as moths, stink bugs, flies, mosquitoes, and beetles, are positively phototactic. Positive phototaxis is seen in these insects. On the other hand, some bugs and insects, such as cockroaches and bed bugs, avoid light sources and hence have negative phototaxis and are negatively phototactic.

Because they prefer the dark to the light, if you turn on the light in your kitchen and there are a few cockroaches crawling around, they will most likely scurry off into a dark corner. Scientists have proposed several hypotheses. One such argument is that they are driven to light because insects utilize moonlight as a navigational tool to avoid predators and other potential risks. The insect either stays straight or travels at an angle relative to the light source. This angle remains constant since the moon is so far away, but it does not apply to smaller light sources such as lightbulbs, porch lights, street lamps, and so on.