How Many Eyes Do Flies Have: Facts About Flies

A fly has two large compound eyes, but that is merely the surface appearance. The scientific reality is that each compound eye has thousands of individual lenses that cluster together to form an ingenious visual masterpiece. In addition, flies have three small triangular simple eyes called ocelli.

Below, we will discover facts about fly eyes.

A Fly Has Thousands of Lenses 

A Fly Has Thousands of Lenses 

Unlike humans with only two eye lenses, one on each eye, flies have thousands of lenses on each compound eye. These lenses work together to create one large but not crisp image of the world.

The lenses allow flies to capture the slightest movement from any direction. This unique ocular setup means that flies can sense danger from the left-right, front, and above and fly away without worrying.

Ommatidia Provides Acute Vision for Flies

Ommatidia is the cluster of photoreceptors cells found in the compound eyes of insects. These are a thousand eyes of the flies. Ommatidia are responsible for collecting the light and filtering it through the lenses. The light-sensitive structures in the flies’ compound eyes have specialized zones that provide them with acute vision. 

Each ommatidium has several photoreceptors that allow the compound eyes to create a 360-degree mosaic image. The three-dimensional images are responsible for flies catching their prey and making it difficult for us to catch them.

Flies Have Simple Eyes Called Ocelli

In between their compound eyes, flies have three triangular-shaped simple eyes called Ocelli used for navigation purposes. The ocelli eyes are specialized in detecting the movement of any object, thereby acting as a compass to keep track of sunlight and help flies move towards the light.

A Flies Vision Is Like a Mosaic 

Unlike humans, who can focus on a particular object, flies cannot make one solid view. Each simple eye in a fly makes a view, and all the tiny images are converged together to make one visual image. Therefore, a fly’s vision can be linked to a mosaic

Instead of moving their eyes, flies receive different information from various points simultaneously.

Flies Detect Motion

Flies will take off at the slightest flinch. Their vision is nowhere close to being effective as humans, but they effortlessly detect form and movement. Flies will quickly react to time and their agility regardless of not necessarily seeing the moving object. 

Flies Can See Behind Them

Ever wondered why it is so difficult to swat a fly? Well, the fly’s eyes are immobile, but their position and spherical shape provide them with a 360-degree field of view, allowing them to see even behind them.

Flies Have No Pupil

Flies are forever flying toward the light but cannot control the amount of light penetrating their eyes with no pupil. Therefore, having no control over the amount of light passing through their eye lens, flies cannot focus on the image they see. 

Flies Can Detect Polarized Light

Flies are able to see polarized light in which the wave travels in a single plane. Unlike humans, flies have the ability to differentiate between polarized and unpolarized light. They are also short-sighted, meaning they only see a visible range of a few yards, which is good for insects. 


As annoying as flies are, we all agree their bizarre compound eyes are pretty cool. The two eyes are well developed to detect motion and save them from danger. Compound eyes in flies also enable them to have a 360 degrees view all the same time. That’s not all; unlike human beings, their compound eyes allow flies to see even behind them. 


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