Generally animals and plants are attracted towards light. This tendency is termed phototropism or photo taxis. Animals which towards the source of light are known as positively phototropic and others that shun light are called negatively phototropic. Most of the insects are positively phototropic but the degree of attraction differs. And some are negatively phototropic. Bed bug shows negative phototropism. Mosquitoes shun intense light, but in dim light they display positive phototropism. This behaviour differs in different species of insects with the exhibition of the following traits.
Insects without eyes also exhibit phototropism. The photosensitivity is distributed or diffused throughout the dorsal surface of insects so photo stimulation can occur even if the insect does not possess any eyes. Some insects are more sensitive to light rays. Their surface cells and eyes are more refined to perceive and follow light sources.
Some are attracted towards yellow light and some towards mercury light etc. well illuminated areas are used as mating grounds by male insects, full of matured sperms and females with matured eggs.