Simple eyes help insects detect close range objects. This term is used to define eye structures that aren’t compounded, or otherwise more complicated. As its title suggests, simple eyes don’t have the additional structures that are used for seeing far range, such as corneas. All adult insects have simple eyes, including some species of nymphs and naiads, such as dragonflies. Honey bees, in particular, have three simple eyes located just above their compound eyes.
The Compound Eyes
Like all adult insects, honey bees have both compound and simple eyes. A honey bee’s compound eyes give him the ability to detect movement, which is why he’s more drawn to a flower in motion than a stationary one. Of his two eye types, a honey bee’s compound eyes help him to collect visual information and recognize color. This is due to the compound eyes’ complicated design. These eyes are made up of a lens and a cone, as well as pigment cells and visual cells.
The Ocelli Eyes
A honey bee has three ocelli eyes, or as they’re better known “simple eyes.” Located on the top of the bee’s head, the ocelli eyes are designed to help the honey bee orient himself with the sun. The honey bee is able to collect and focus sunlight through his ocelli eyes’ single lens. Set in a triangle, on the top of his head, the two outer ocelli eyes are called dorsal ocelli, while the middle is referred to as the central ocelli. Although quite sensitive to light, and invaluable to direction, the honey bees’ ocelli eyes cannot resolve images.
Compound and Simple Eyes: You Can’t Have One Without the Other
Honey bees, like all other adult insects, cannot rely on only one set of eyes. The two eye sets, compound and ocelli, work harmoniously to keep the busy bee on the right path. By themselves, the simple eyes aren’t capable of producing any sort of motor response. No matter how blinding the sunlight, the bee would feel no sense of direction if he didn’t also have his compound eyes. The compound eyes work as a sort of receptor, able to take the stimuli provided from the simple eyes and process it, generating an effect on the nervous system that determines direction and other motor responses.
Detecting the Simple Eye
Fully developed adult insects will always have ocelli, so long as they also have compound eyes. The two go hand-in-hand, working in conjunction with one another to detect changes in light, determine direction and collect and process visual information. In general, ocelli eyes will be located on the adult insect’s back or face. Unlike the prominent compound eyes, ocelli eyes appear as 2 – 3 tiny bulges, making them slightly difficult to detect when they’re located away from the face, such as along the insect’s back.