The intricate design of the insect’s compound eyes are wonders to behold, and has provided a keen, movement-oriented vision for these little critters for millions of years!

As you have probably already guessed, insects see very differently than we do. Insect vision is designed to detect movement, not necessarily the sharpness of images. However the large round shape of compound eyes, made up of many specialized zones called ommatidia, allows for a much wider angle of view than single-aperture eyes. That’s why houseflies seem to see behind their heads! These are the specialized eyes that support their speed, particularly with flying insects. The lightning-quick dragonfly, for instance, has about 30,000 ommatidia in each eye!

Also, while compound eyes are generally not designed for resolution, the eyes of honey bees, dragonflies and of course the mantid are somewhat enhanced. The zones of the eyes are arranged in an area called fovea for acute vision and allows more light to be received for a higher resolution.

For instance, a dragonfly can detect the movement of small prey several feet away while flying. Similarly, the vision of the praying mantis is much sharper than many insects, having a good field of vision of objects about 50 feet away.

That is not too bad, considering that some flies and mosquitoes can only see clearly objects a few millimeters away. I guess you don’t need to see very far when your primary job is to suck blood from human flesh! As far as distance is concerned, the healthy human eye can still see further out than a mantis, even proportionately, but again we don’t have the wide field of vision and reflexive detection of movement that the mantid has.

The two main types of compound eyes are the apposition and superposition. Basically, the apposition type has a smaller field of vision during the night and the superposition has a wider and brighter field. The resolution of the superposition, however, is not as high as the apposition.

Generally diurnal (daytime) insects have apposition eyes, while nocturnal (nighttime) has the superposition. But is possible some are able to transition from one phase to the other by adjustment of pigment of the ommatidia.

Since the mantid is primarily a diurnal insect, its nighttime vision is not as keen as during the day, as they do most of their hunting during the light hours.

Curiously enough, one of the mantids we kept naturally had brown eyes during the day which turned to near black at night whether or not we had the light on in the room. Could this have been a transition from apposition to the superposition phase of the compound eyes? I don’t have the answer to that, but I will post it as soon as I find out. Feel free to send the answer if you find out before I do!

By Noy Ilao