Although bed bugs love to feed on human blood, they do not have eyes that see like humans. 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 bug’s eye is made up of hundreds of lenses called facets that fit together in a hexagonal structure. An easy way to imagine what this bug eye looks like is to think of a honeycomb that is conical in shape and not flat. It’s like a soccer ball, but on a smaller and more complex level. The individual facets consist of two lenses, one on the surface and one on the inside. Bed bugs’ double-lens eye structure allows them to see in 3-D. All these facets fitted together make up the eye of the parasite. These facets are connected to tubes that focus light onto a central structure called a rhabdome. The rhabdome is sensitive to light and directs the information through an optic nerve to the insect’s brain.
Each individual facet in the bed bugs eye sends a different image to its brain. When all these images are processed and put together, a mosaic is created. This three-dimensional mosaic is how the bedbug can see its human host. It is not known whether, as the bed bug moves, the image it sees is updated in its entirety or whether it takes microseconds for each lens to update the visual information. If this parasitic insect’s vision were updated lens by lens, it would see a constantly updating image. This view would be like looking through a kaleidoscope with 3-D glasses.
Bed bugs come out at night or in the dark to feed on their human hosts for a couple of reasons. One of the reasons is because at night when you are sleeping in your bed, you won’t feel them crawling over you and biting you. Another reason could be that these bloodsuckers have light-sensitive eyes that allow them to see better in the dark. These compound eyes can also pick up a heat signature from the human body. This is why most bed bug bites occur in the center of mass part of your body. Its heat signature is warmer in the torso, legs, and arms than it is in the fingers and toes.
Humans may have color vision that is constantly updated, while bed bugs’ compound eyes see in black and white. Your eyes also don’t constantly update the entire image at once, but they can see just fine to do the job they’re best at. That job is to find a human host on which to feed on its blood.