Mantids have triangular heads with large compound eyes and three simple eyes (ocelli) in a triangular arrangement between the antennae. Considerable research has been done on the mantis' eyesight. It has been shown that this insect is capable of stereoscopic vision, allowing it to accurately gauge distances as do most mammalian predators; it uses the extreme mobility of its head (a mantis can turn its head fully 180 degrees, and their vision covers 300 degrees) to use parallax (the apparent movement of an object against a more distant background) as a reinforcement to the binocular triangulation.

The compound eyes themselves are a work of art - their faceted nature always presents the appearance of a black pupil pointed directly at you. It is such a convincing optical illusion that it was only recently that I even took note of it and made myself think about the fact that mantids do not have eyeballs or pupils. In addition to this curious feature, the entire surface of the eyes change color according to the amount of ambient light - they are light green or tan in sunlight, and chocolate brown at twilight or in low light conditions. Many other arthropods also exhibit illusory pupils in their compond eyes.