In addition to having multiple legs, you may have noticed that insects possess multiple eyes as well. Considering this trait, it goes without saying that insects do not see the world in the way humans do. Since insects possess several eyes, you may be inclined to assume that their eyesight is superior to a humans. But given the many significant differences between the types of eyes that exist in nature, making a cut and dry comparison between insect eyes and human eyes is not so easy to do. In some aspects, such as color recognition, humans usually have superior vision, but many insects are capable of perceiving 360 degrees of their surrounding environment, which would be like a human having eyes on the back of his/her head. Many insects can also perceive ultraviolet light, which is entirely invisible to the human eye. It is also true that the eyesight of insects differ tremendously from species to species in terms of acuity, depth perception, color recognition and many other factors.
Most insect species have two types of eyes, simple and compound. A simple eye, which is referred to as ocello (singular) and ocelli (plural), is a small eye that is made of just one lens. Compound eyes are the larger eyes that can be seen bulging on either side of an insect’s head. These eyes contain many small lenses, sometimes thousands. Adult insects have one set of compound eyes, but many people fail to take note of the three ocelli located in a triangular formation on the top of an insect’s head. Insects that undergo a complete metamorphosis, like butterflies, beetles and flies, are born only with ocelli and no compound eyes. For these insects, compound eyes become fully developed in adulthood. Insects that undergo incomplete metamorphosis, like grasshoppers, stink bugs, dragonflies and mayflies, have both ocelli and compound eyes during their nymphal stage and into adulthood. The ocelli perceive light and movement, while compound eyes provide a general, but not detailed, panoramic picture of the surrounding environment. Most parasitic insects, such as fleas, have only ocelli and no compound eyes, as their tiny environment makes compound eyes unnecessary.
Have you ever noticed a triangular pattern of tiny eyes on the top of an insect’s head?