Although bed bugs love feeding on human blood they do not have eyes that see like human beings. These parasitic creatures have what is called a compound eye structure. It is thought that they do not see in color, that they visualize in black and white.
A bed bugs eye is made up of hundreds of eye lenses called facets that fit together in a hexagon structure. An easy way to picture what this insects eye looks like is to think of a bee honey comb in a conical shape and not flat. It is like a soccer ball, but on a smaller, more complex level. The individual facets consist of two lenses, one on the surface and one on the inside. The bed bugs dual lens eye structure allows it to see in 3-D. All of these facets fitted together construct the parasites eye. These facets are connected to tubes that focus light down a central structure called the rhabdome. The rhabdome is light sensitive and directs the information through an optic nerve to the bugs brain.
Each individual facet in the bed bugs eye sends a different picture to it’s brain. When all these pictures are processed and put together a mosaic is created. This 3-D mosaic is how the bed bug can see it’s human host. It is not known if, as the bed bug moves, the picture it sees updates on a whole or takes micro-seconds for each lens to update the visual information. If this parasitic insect’s vision updates lens by lens then it would see a constantly updating picture. This view would kind of be like looking through a kaleidoscope with 3-D glasses on.
Bed bugs come out at night or in the dark to feed on their human hosts for a couple of reasons. One reason is because at night, when you are in your bed sleeping, you won’t feel them crawling on you and biting you. Another reason could be that these blood suckers have light sensitive eyes that enable them to see better in the dark. These compound eyes can also pick up a heat signature of the human body. This is why the majority of bed bug bites occur on the center of mass part of your body. Your heat signature is warmer on your torso, legs, and arms than it is on your fingers and toes.
Humans may have color vision that updates constantly where as bed bugs compound eyes see in black and white. Their eyes also do not constantly update the full picture at once, but they can see very well to do the job they are best at. That job is to find a human host in which to feed off of their blood.