House Fly Eyes
House fly eyes are compound organs that are comprised of thousands of individual lenses. Compound eyes are capable of detecting both the polarization of light and color spectrums unseen by humans.
House fly eyes can recognize even the slightest movements in a full, 360-degree spectrum. This allows the fly to see a far wider range, as well as detect and react to movement at a quicker pace than species with simple eyes. This is the reason that it is extremely difficult to swat a housefly. One tactic that may prove successful is to swat at the fly simultaneously with two objects: this confuses the receptors of the housefly.
Houseflies are meticulous in their grooming, particularly around their eyes. These flies use their forelegs to remove any material that has come into contact with the eyes.
Dichotomous Key for a House Fly