How many frames per second a fly sees and how many eyes it has. Compound eyes Modern scientific developments

The question "How many eyes does a common fly have?" not as simple as it seems. Two large eyes located on the sides of the head can be seen with the naked eye. But in fact, the device of the fly's organs of vision is much more complicated.

If you look at the enlarged image of the eyes of a fly, you can see that they are similar to honeycombs and are made up of many individual segments. Each of the parts has the shape of a hexagon with regular edges. This is where the name of such an eye structure came from - facet ("facette" in French means "edge"). Many and some arthropods can boast of complex compound eyes, and the fly is far from the champion in the number of facets: it has only 4,000 facets, and dragonflies have about 30,000.

The cells we see are called ommatidia. Ommatidia are cone-shaped, the narrow end of which extends deep into the eye. The cone consists of a cell that perceives light and a lens protected by a transparent cornea. All ommatidia are closely pressed to each other and connected by the cornea. Each of them sees "their" fragment of the picture, and the brain adds these tiny images into one whole.

The location of the large compound eyes differs between female and male flies. In males, the eyes are close-set, while in females they are more spaced apart, since they have a forehead. If you look at a fly under a microscope, then in the middle of the head above the faceted organs of vision, you can see three small dots arranged in a triangle. In fact, these points are simple eyes.

In total, the fly has one pair of compound eyes and three simple ones - a total of five. Why did nature take such a difficult path? The fact is that faceted vision has been formed in order to first of all cover as much space as possible with a glance and catch movement. These eyes perform the main functions. With simple eyes, the fly was "provided" to measure the level of illumination. Compound eyes are the main organ of vision, and simple eyes are secondary. If the fly did not have simple eyes, it would be slower and could only fly in bright light, and without compound eyes it would be blind.

How does a fly see the world?

Large convex eyes allow the fly to see everything around it, that is, the viewing angle is 360 degrees. It is twice as wide as a human. The fixed eyes of the insect look simultaneously on all four sides. But the visual acuity of a fly is almost 100 times lower than that of a human!

Since each ommatidium is an independent cell, the picture is reticulated, consisting of thousands of separate small images that complement each other. Therefore, the world for a fly is an assembled puzzle, consisting of several thousand pieces, and rather vague. More or less clearly, the insect sees only at a distance of 40 - 70 centimeters.

The fly is able to distinguish colors and even polarized light and ultraviolet invisible to the human eye. The eye of a fly senses the slightest change in the brightness of the light. She is able to see the sun hidden by thick clouds. But in the dark, flies see poorly and lead a predominantly diurnal lifestyle.

Another interesting ability of the fly is a quick reaction to movement. A fly perceives a moving object 10 times faster than a human. It easily "calculates" the speed of an object. This ability is vital for determining the distance to the source of danger and is achieved by "transferring" the image from one cell - ommatidium to another. Aeronautical engineers have adopted this feature of the fly's vision and developed a device for calculating the speed of a flying aircraft, repeating the structure of its eye.

Thanks to this fast perception, flies live in a slow-motion reality compared to us. A movement lasting a second, from a human point of view, is perceived by a fly as a ten-second action. Surely people seem to them very slow creatures. The insect brain works at the speed of a supercomputer, receiving an image, analyzing it and transmitting the appropriate commands to the body in thousandths of a second. Therefore, it is not always possible to swat a fly.

So, the correct answer to the question "How many eyes does a common fly have?" will be the number five. The main ones are a paired organ in a fly, like in many living creatures. Why nature created exactly three simple eyes remains a mystery.

Even in early childhood, many of us asked such seemingly trifling questions about insects, such as: how many eyes does an ordinary fly have, why does a spider weave a web, and a wasp can bite.

The science of entomology has answers to almost any of them, but today we will call on the knowledge of nature and behavior researchers in order to deal with the question of what the visual system of this species is.

In this article, we will analyze how a fly sees and why it is so difficult to slap this annoying insect with a fly swatter or catch it with a palm on the wall.

room resident

The housefly or housefly belongs to the family of real flies. And although the topic of our review concerns all species without exception, we will allow ourselves, for convenience, to consider the entire family using the example of this very well-known type of home parasites.

The common house fly is a very unremarkable external insect. It has a gray-black coloration of the body, with some hints of yellowness in the lower part of the abdomen. The length of an adult rarely exceeds 1 cm. The insect has two pairs of wings and compound eyes.

Compound eyes - what's the point?

The visual system of the fly includes two large eyes located at the edges of the head. Each of them has a complex structure and consists of many small hexagonal facets, hence the name of this type of vision as facet.

In total, the fly's eye has more than 3.5 thousand of these microscopic components in its structure. And each of them is able to capture only a tiny part of the overall image, transmitting information about the received mini-picture to the brain, which collects all the puzzles of this picture together.

If you compare facet vision and binocular vision, which a person has, for example, you can quickly make sure that the purpose and properties of each are diametrically opposed.

More developed animals tend to concentrate their vision on a certain narrow area or on a specific object. For insects, it is important not so much to see a specific object as to quickly navigate in space and notice the approach of danger.

Why is she so hard to catch?

This pest is really very difficult to take by surprise. The reason is not only the increased reaction of the insect in comparison with a slow person and the ability to break away almost instantly. Mainly, such a high level of reaction is due to the timely perception of changes and movements in the brain of this insect within the viewing radius of its eyes.

The fly's vision allows it to see almost 360 degrees. This type of vision is also called panoramic. That is, each eye gives a 180-degree view. This pest is almost impossible to take by surprise, even if you approach it from behind. The eyes of this insect allow you to control the entire space around it, thereby providing one hundred percent all-round visual defense.

There is another interesting feature of the fly's visual perception of the color palette. After all, almost all species differently perceive certain colors that are familiar to our eyes. Some of them insects do not distinguish at all, others look different to them, in other colors.

By the way, in addition to two compound eyes, the fly has three more simple eyes. They are located in the interval between the faceted ones, on the frontal part of the head. Unlike compound eyes, these three are used by insects to recognize one or another object in close proximity.

Thus, to the question of how many eyes an ordinary fly has, we can now safely answer - 5. Two complex faceted, divided into thousands of ommatidia (facets) and designed for the most extensive control over changes in the environment around it, and three simple eyes , allowing, as they say, to focus.

World view

We have already said that flies are color blind, and either do not distinguish all colors, or they see objects familiar to us in other color tones. Also, this species is able to distinguish ultraviolet.

It should also be said that for all the uniqueness of their vision, these pests practically do not see in the dark. At night, the fly sleeps, because its eyes do not allow this insect to trade in the dark.

And yet these pests tend to perceive well only smaller and moving objects. An insect does not distinguish between such large objects as a person, for example. For a fly, this is nothing more than another part of the interior of the environment.

But the approach of a hand to an insect is perfectly captured by its eyes and promptly gives the necessary signal to the brain. Just like any other rapidly approaching danger, it will not be difficult for these rogues, thanks to the sophisticated and reliable tracking system that nature has provided them with.

Conclusion

So we analyzed what the world looks like through the eyes of a fly. Now we know that these ubiquitous pests, like all insects, have an amazing visual apparatus that allows them not to lose vigilance, and in the daytime to keep all-round observational defense one hundred percent.

The vision of the common fly resembles a complex tracking system, including thousands of mini-surveillance cameras, each of which provides the insect with timely information about what is happening in the immediate range.

The eye of an insect at high magnification looks like a small lattice.

This is because the insect's eye is made up of many small facets. The eyes of insects are called faceted. A tiny eye-facet is called ommatidium. Ommatidium has the form of a long narrow cone, the base of which is a lens that looks like a hexagon. Hence the name of the compound eye: facette translated from French means "edge".

A bundle of ommatidia makes up a complex, round, insect eye.

Each ommatidium has a very limited field of view: the viewing angle of ommatidia in the central part of the eye is only about 1°, and at the edges of the eye - up to 3°. Ommatidium "sees" only that tiny section of the object in front of his eyes, to which he is "aimed", that is, where the continuation of its axis is directed. But since the ommatidia are closely adjacent to each other, and their axes in the round eye diverge like rays, the entire compound eye embraces the object as a whole. Moreover, the image of the object is obtained in it as a mosaic, that is, composed of separate pieces.

The number of ommatidia in the eye varies in different insects. A worker ant has only about 100 ommatidia in its eye, a housefly has about 4,000, a worker bee has 5,000, butterflies have up to 17,000, and dragonflies have up to 30,000! Thus, the vision of an ant is very mediocre, while the huge eyes of a dragonfly - two iridescent hemispheres - provide a maximum field of view.

Due to the fact that the optical axes of ommatidia diverge at angles of 1-6°, the image clarity of insects is not very high: they do not distinguish fine details. In addition, most insects are nearsighted: they see surrounding objects at a distance of only a few meters. But the compound eyes are perfectly able to distinguish flickering (blinking) of light with a frequency of up to 250–300 hertz (for a person, the limiting frequency is about 50 hertz). The eyes of insects are able to determine the intensity of the light flux (brightness), and in addition, they have a unique ability: they can determine the plane of polarization of light. This ability helps them navigate when the sun is not visible in the sky.

Insects see colors, but not in the same way as we do. For example, bees "do not know" red and do not distinguish it from black, but they perceive ultraviolet rays invisible to us, which are located at the opposite end of the spectrum. Some butterflies, ants and other insects also distinguish ultraviolet light. By the way, it is precisely the blindness of the pollinating insects of our strip to the red color that explains the curious fact that among our wild flora there are no plants with scarlet flowers.

The light coming from the sun is not polarized, that is, its photons have an arbitrary orientation. However, passing through the atmosphere, the light is polarized as a result of scattering by air molecules, and in this case, the plane of its polarization is always directed towards the sun.

By the way...

In addition to compound eyes, insects have three more simple ocelli with a diameter of 0.03-0.5 mm, which are located in the form of a triangle on the fronto-parietal surface of the head. These eyes are not adapted for distinguishing objects and are needed for a completely different purpose. They measure the average level of illumination, which is used as a reference point ("zero signal") in the processing of visual signals. If these eyes are glued to an insect, it retains the ability to spatial orientation, but can fly only in brighter light than usual. The reason for this is that the glued eyes take the black field as the “middle level” and thus give the compound eyes a wider range of illumination, and this, accordingly, reduces their sensitivity.

Each of us who has at least once tried to get rid of an annoying fly by running after it with a cracker in hand knows perfectly well that this task is not always easy to accomplish, and sometimes even impossible at all. The reaction of a gray-black small tenant is what you need. The fact is that you are not a competitor to her. Why? Read the article in which we will tell you all about winged annoyances.

What is superior to us this fly:

• in the speed of movement (more than twenty kilometers per hour),
• in the ability to keep track of her rapid movements.

How flies see

We, the representatives of the human race, who consider ourselves so perfect and omnipotent, have only binocular vision, which allows us to focus on specific object or in a certain narrow area in front of us, and are in no way able to see what is happening behind us, but for a fly this is not a problem, since its vision is panoramic, it sees the entire space at 360 degrees (each eye is capable of providing a view of 180 degrees).

In addition, these insects, not only due to the anatomical structure of their visual apparatus, can see in different directions at once, but are also able to purposefully survey the space around them. And all this is provided located on the sides with two large convex eyes that stand out well on the head of the insect. Such a huge field of view determines the special "insight" of these insects. In addition, they need significantly less time to identify objects than we humans do. Their visual acuity also exceeds our human 3 times.

The structure of compound eyes

If you look at the eye of a fly under a microscope, you can see that it is composed, like a mosaic, of many small areas - facets - hexagonal structural units, outwardly very similar in shape to honeycombs. Such an eye, respectively called faceted, and the facets themselves are also called ommatidia in a different way. In the eye of a fly, one can count about four thousand such facets. All of them give their image (a small part of the whole), and the brain of a fly forms from them, like from puzzles, a big picture.

Panoramic, faceted vision and binocular vision, which is characteristic of people, have a diametrically opposite purpose. For insects to be able to quickly navigate and not only notice the approach of danger, but also to have time to avoid it, it is important not to see a specific object well and clearly, but, mainly, to carry out timely perception of movements and changes in space.

There is another curious feature of the fly's visual perception of the world around it, regarding the color palette. Some, so familiar to our eyes, of which insects do not distinguish at all, others look different to them than to us, in other tones. As for the beauty of the surrounding space - flies distinguish not only the seven primary colors, but also their subtlest shades, because their eyes are able to see not only visible light, but also ultraviolet, which, alas, people cannot see. It turns out that in the visual perception of the fly, the world around is more iridescent than that of humans.

It should also be noted that, having certain advantages of the visual system, these representatives of the six-legged world (yes, they have 3 pairs of legs) cannot see in the dark. At night, they sleep, as their eyes do not allow them to navigate in the dark.

And these small and nimble creatures notice only medium-sized and moving objects. An insect does not perceive such a large object, for example, as a person. And here the approach of a human hand to a fly, its eyes see perfectly and immediately transmit the necessary signal to the brain. Also, any other rapidly approaching danger will not be difficult for them to see, thanks to the complex and reliable structure of the eyes, which allows the insect to see space in all directions at the same time - right, left, up, back and forth and react accordingly, saving itself, which is why they are so difficult slap.

Numerous facets allow the fly to follow very fast moving objects with high image clarity. For comparison, if a person's vision can perceive 16 frames per second, then a fly has 250-300 frames per second. This property is necessary for flies, as already described, to catch movements from the side, as well as for their own orientation in space during a fast flight.

number of eyes in a fly

By the way, in addition to two large complex compound eyes, the fly has three more simple, located on the forehead heads in the interval between the faceted ones. In contrast to the compound eye, these three are needed in order to see objects at close range, since the compound eye in this case is useless.

Thus, when asked how many eyes a housefly has, we can now accurately answer that there are five of them:

• two faceted (complex), consisting of thousands of ommatidia and necessary to obtain information about events rapidly changing in space,
• and three simple eyes, allowing, as it were, to focus.

Compound eyes are located in flies on the sides of the head, moreover, in females, the location of the organs of vision is somewhat expanded (separated by a wide forehead), while in males, the eyes are slightly closer to each other.

All people know that it is very difficult to catch or swat a fly: it sees very well and instantly reacts to any movements, flying up. The answer lies in the unique vision of this insect. The answer to the question of how many eyes a fly has will help to understand the reason for its elusiveness.

The device of the visual organs

The house or common fly has a black-gray body color up to 1 cm long and a slightly yellowish abdomen, 2 pairs of gray wings and a head with large eyes. It belongs to the most ancient inhabitants of the planet, as evidenced by the data of archaeologists who discovered specimens dating back 145 million years.

When examining the head of a fly under a microscope, you can see that it has very original voluminous eyes located on both sides. As you can see in the photo of the fly's eyes, they visually look like a mosaic composed of 6-sided structural units, which are called facets or ommatidia, similar to the structure of honeycombs. Translated from French, the word "fasette" means facets. Because of this, the eyes are called faceted.

How to understand what a fly sees compared to a person whose vision is binocular, that is, it is made up of two pictures that 2 eyes see? In insects, the visual apparatus is more complex: each eye consists of 4 thousand facets, showing a small part of the visible image. Therefore, the formation of a general picture of the external world in them occurs according to the principle of “collecting puzzles”, which allows us to speak about the unique structure of the brain of flies, capable of processing more than 100 frames of images per second.

On a note!

Facet vision is not only in flies, but also in other insects: bees have 5 thousand facets, butterflies - 17 thousand, dragonflies record holders - up to 30 thousand ommatidia.

How a fly sees

Such a device of the visual organs does not allow the fly to concentrate on a particular object or object, but shows a general picture of the entire surrounding space, which allows you to quickly notice the danger. The viewing angle of each eye is 180°, which together is 360°, i.e. the type of vision is panoramic.

Thanks to this structure of the eyes, the fly perfectly surveys everything around, including seeing a person who is trying to sneak up behind. Control over the entire surrounding space provides her with 100% defense against all troubles, including from people gathering.

In addition to the 2 main ones, the flies have 3 more ordinary eyes located on the forehead in the intervals between the faceted ones. These organs allow them to view nearby objects more clearly for recognition and immediate reaction.

Interesting!

Summarizing all the data, we can state that the vision of a fly is represented by 5 eyes: 2 faceted ones - to control the surrounding space and 3 simple ones - for focusing and recognizing objects.

Features of the visual abilities of flies

The vision of the common fly has many more interesting features:

• flies distinguish the main colors and their shades perfectly, besides, they are able to distinguish ultraviolet rays;
• they see absolutely nothing in the dark and therefore sleep at night;
• however, they capture some colors from the entire palette a little differently, therefore they are conditionally considered color blind;
• the faceted device of the eyes allows you to fix everything at the same time at the top, bottom, left, right and in front and makes it possible to quickly respond to an approaching danger;
• the eyes of a fly distinguish only small objects, for example, the approach of a hand, but they do not perceive a large figure of a person or furniture in a room;
• in males, the compound eyes are closer together than in females, which have a wider forehead;

Interesting!

Visual acuity is also evidenced by the fact how many frames per second a fly sees. For comparison, exact numbers: a person perceives only 16, and a fly - 250-300 frames per second, which helps her to navigate perfectly at a fast speed in flight.

Flicker characteristics

There is an indicator of visual abilities, which is associated with the frequency of flickering of the image, i.e. its lowest limit, at which light is fixed as a constant source of illumination. It is called CFF - critical flicker-fusion frequency. Its value indicates how quickly the animal's eyes are able to update the image and process visual information.

A person is able to detect a flicker frequency of 60 Hz, that is, an image update 60 times per second, which is followed when displaying visual information on a television screen. For mammals (dogs, cats), this critical value is 80 Hz, which is why they usually do not like watching TV.

The higher the flicker frequency value, the more biological advantage the animal has. Therefore, for insects, in which this value reaches 250 Hz, this manifests itself in the possibility of a faster reaction to danger. After all, for a person approaching the “prey” with a newspaper in his hands with the intention of killing her, the movement seems fast, but the unique structure of the eye allows it to capture even instantaneous movements, as if in slow motion.

According to biologist K. Gili, such a high critical flicker frequency in flies is due to their small size and fast metabolism.

Interesting!

The difference in the CFF index for different species of vertebrates looks like this: the smallest 14 Hz is in eels and turtles, 45 in reptiles, 60 in humans and sharks, in birds and dogs - 80, in ground squirrels - 120.

The above analysis of visual abilities allows us to understand that the world through the eyes of a fly looks like a complex system of a large number of pictures, by analogy with small video cameras, each of which transmits information to the insect about a small part of the surrounding space. The assembled image allows you to keep a visual "all-round defense" at a glance and instantly react to the approach of enemies. Research scientists of such visual abilities of insects have allowed the development of flying robots, in which computer systems control the position in flight, simulating the vision of flies.