What do you mean?
They have eyes so they can see if there is light around or not..
Indeed, eyes can be used for both perception of forms and intensity of ligth (and thus perception of a light or dark environment) but invertebrates can also have specific receptors for the intensity of light.
From this post http://www.macrostylis.com/en/articles/ … ptors.html
it seems that some insect larvae can even perceive the intensity of light from organs in the trunk, although I do not know if it is the case for cockroaches and mosquitoes..
How do cockroaches and mosquitoes know the difference between light and dark?
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