How many eyes does a spider have on average? The amazing eyes of jumping spiders

Did you know?It is the compound eyes that are responsible for the perception of color in insects.

Not all types of spiders have facets. It is believed that these rudiments were left to spiders by their ancestors - chelicerates, which had a faceted eye structure. Such organs are also capable of detecting and reflecting light. In the structure of the lateral auxiliary organs of perception, the layer of nerve cells is much closer to the light flux than the light-sensitive cells. This creates blind spots where the optic nerve attaches, but at the expense large quantity organs, this deficiency does not create inconvenience.

What is the power of their vision?

The ability to distinguish between the strength and direction of light allows the spider to track the direction of movement of its prey. This is especially important for those who weave webs.

Important!The movement of objects is recorded by the side eyes, then the spider turns to the target and can examine it in close-up with the help of the main ones. Without lateral additional organs of vision, he will not be able to hunt.

The advantages of spider vision can also be called the following:

• better picture detail than a person;
• ability to see close-up;
• Spiders see objects close to them better than objects at a distance of more than 10 cm;
• ability to see in the ultraviolet spectrum;
• ability to perceive polarized light;
• the ability to follow prey in any direction around you;
• eyes help to move quickly in the grass;
• the spider does not miss when jumping for prey, which means it can very accurately determine the distance.

Peculiarities

A large number of eyes allows the spider to see almost around itself. In addition to them, the spider has sensitive hairs on its legs, with which it “hears movement,” complementing the visual picture of the world.

Important!Brazilian banana spider- the most aggressive of the hunting species. Its poison is fatal to humans, and this hunter attacks any moving object.

Features of spider vision are:

• number of organs;
• each eye sees a separate picture, but for the spider it combines into one whole;
• different structures of the main and additional organs.

So, knowing the spider’s habitat and its species, we can draw conclusions about how many eyes it has and how it can see. Without such information, our understanding of arachnids will be far from complete.

The variety of spiders on Earth amazes even the most inquisitive, because science has found more than 42 thousand species, and you can easily add thousands of arachnid fossils to this figure. The habitats of farts are very diverse: many species can live not only on land, but even on water.

Spiders are interesting not only for this. They exist as vegetarians, harmless to other living beings; and poisonous, capable of killing a person in a few hours. This type of insect has been living among us for over 100 million years, has a unique external structure, an interesting texture, but its organ of vision is worthy of special attention: the number of eyes in each species and their features.

How many eyes do spiders have?

There are specialists who study the field of animal vision, these are zoophthalmologists, who, having heard such interest Ask, will not give an exact answer. At a minimum, you need to know what species the insect is. After all, in fact, everything is different: the number of eyes can vary depending on the genus and species. In most cases, this figure will be 4, but there are species that have 6, 8, and also known owners of 12 eyes.

The fact is that in the process of evolution, nature awarded each species of insect with exactly the number of eyes, the power of vision that was necessary for survival in the habitat where they developed. For example, at different poles of the globe there are cave species, their visual power is very low and they are almost blind, but on the surface there are jumping spiders whose visual power is comparable to that of a human, and they are even able to distinguish some colors.

Types of eyes

In all species, the organs of vision are arranged in two rows, and they are responsible for different functions:

1. The front pair is aka medial- responsible for basic vision.
2. Other pairs of eyes are called side effects- they are responsible mainly for all other functions, as well as to warn the insect about approaching danger.
3. Just like other insects there are compound eyes, which have separate areas responsible for certain functions, but in spiders these are special additional pairs of eyes, because of this they may have more than 4 eyes.

The power of spiders' vision

The front pair of spiders' eyes are capable of seeing things that even humans cannot discern. Research has been conducted and it has been proven that some types of spiders have the ability to sense even ultraviolet light. For example:

Features of the eyes

All individuals differ not only in the number of eyes, but also in characteristic difference buildings, execution various functions organs of vision. For example, the family of individuals is of great interest to zoophthalmologists Salticidae, because in this species the front or, as they also say, the main, main pair of eyes, has the largest lens among other species, that is, the very shape of the organs of vision is similar to the structure of a spyglass.

Scientists have found a pattern that, regardless of the number of eyes, be it cross spiders, crab spiders, sand spiders or other species, everyone’s organ of vision functions as a single whole. This is expressed as follows:

1. First of all, the lateral or rear eyes are included in the work; they find a potential victim another 20–30 cm before its approach.
2. In the second stage, the main eyes are included in the work; It is they who convey information and the main focus, determining whether the object of the hunt is ahead, or some foreign object that does not need to be paid attention to.

Interesting facts related to sensory

In addition to eyes, spiders also have separate organs for interacting with the environment in which they live. For example, all species do not have ears; the insect can hear only due to the tiny thrichobotria hairs that are found on its limbs. These hairs, as an organ of hearing, allow the spider to determine with millimeter accuracy where the source of sound emission and air movement is located. Also, this organ on the limbs allows you to capture taste. We can conclude that spiders do not have receptors responsible for taste in the mouth, and they receive all the information about their prey, whether it is suitable for food, through these same special hairs on their legs.

Having learned even such brief information about the structure of vision, it is impossible to give a definite answer as to how many eyes spiders have. After all, in order to answer this question more specifically, you need to, at a minimum, find out the spider’s habitat, or better yet, what species and subspecies it belongs to. If you have all the information about the spider, you can accurately answer how many eyes it has.

Range and habitats

Spiders live everywhere to the globe, but in warm regions there are the most species. Almost all spiders are terrestrial animals. The exception is the silverback spider, which lives in water. A number of spider species hunt on the surface of the water. Some spiders build nests, shelters and burrows, while others do not permanent place a habitat. For the most part, spiders are nocturnal animals.

Description

Arachnida (Arachnida) is a class of arthropods that includes spiders, mites, scorpions and other lesser-known subtypes of chelicerates. Scientists estimate that more than 100,000 species of arachnids live on the planet today. Arachnids have two main body sections (the cephalothorax and abdomen) and four pairs of legs. Arachnids differ from insects in that they lack wings and antennae.

It should be noted that some orders of arachnids, for example, mites and ricinules, have only three pairs of legs in the larval stage, and the fourth appears in the nymphal stage. Arachnids have an exoskeleton that periodically moults to allow the animal to grow. In addition to four pairs of legs, they have two additional pairs of appendages (chelicerae and pedipalps) which they use for various purposes such as feeding, defense, locomotion, reproduction or perception. environment. Most arachnid species are terrestrial animals, although some representatives (especially mites) live in fresh and sea water.

Internal construction

In internal structure arachnids secrete nervous, respiratory, digestive, excretory, reproductive system, special venom-bearing and spinning organs. Organization nervous system relatively complex and different different types. Its main feature is the abdominal nerve chain and the brain, which has anterior and posterior sections.

The respiratory organs are the trachea and lung sacs in spiders and representatives of other orders, only tracheas or exclusively pulmonary sacs may be present, which open on the underside of the abdomen with respiratory openings. Tracheas are tubes that penetrate the body of the animal and are adapted for air gas exchange.

The digestive system consists of the esophagus, stomach and hindgut, ending in the cloaca. The ducts of the excretory Malpighian glands flow into the cloaca. All arachnids are dioecious, fertilization is internal, and development is direct. Most species are oviparous, only a few are viviparous. Many arachnids have venom glands and/or arachnoid glands. The latter release liquid, which is drawn into a thread and quickly hardens. Spiders build a fishing net from webs or line their burrows with it.

Types of spiders

Scientists have described more than 42,000 species of spiders. About 2,900 varieties are known in the CIS countries. Let's consider several varieties:

• Blue-green tarantula (lat. Chromatopelma cyaneopubescens)– one of the most spectacular and beautifully colored spiders. The tarantula's abdomen is red-orange, its limbs are bright blue, and its carapace is green. The size of the tarantula is 6-7 cm, with a leg span of up to 15 cm. The spider’s homeland is Venezuela, but this spider is found in Asian countries and in African continent. Despite belonging to tarantulas, this type does not bite spiders, but only marks special hairs located on the abdomen, and only in case of severe danger. The hairs are not dangerous for humans, but they cause minor burns on the skin, similar in effect to nettle burns. Surprisingly, female chromatopelma are long-lived compared to males: the lifespan of a female spider is 10-12 years, while males live only 2-3 years.

• Flower spider (lat. Misumena vatia) belongs to the family of side-walking spiders (Thomisidae). Color varies from absolutely white to bright lemon, pink or greenish. Male spiders are small, 4-5 mm long, females reach sizes of 1-1.2 cm. Species flower spiders distributed throughout European territory(excluding Iceland), found in the USA, Japan, and Alaska. The spider lives on open area, with an abundance of flowering herbs, as it feeds on the juices of butterflies and bees caught in its “embraces”.

• Grammostola pulchra (lat. Grammostola Pulchra)- a type of tarantula spider that natural environment lives only in Uruguay and southern regions Brazil. A rather massive spider, reaching a size of 8-11 cm, with a dark color and a characteristic “metallic” sheen of hairs. In nature, it prefers to live among the roots of plants, but almost never digs its own burrows. Pulhra often becomes a pet among connoisseurs of exotic pets.

• Argiope Brünnich or wasp spider (lat. Argiope bruennichi) – a spider with an unusual coloring of the body and limbs - yellow, black and white stripes, for which it received its name. True, the male wasp spiders are not so bright, and they are smaller in size than the females: the “young ladies” reach a size of 2.5 cm, and together with the legs - 4 cm, but the male rarely grows more than 7 mm in length. The species is widespread in Europe, Asia and southern Russia, in the Volga region and in North Africa. The Argiope spider lives in meadows with an abundance of grass, on the edges of forests. The web of the argiope is very strong, so it is difficult to tear it, it will only stretch under pressure.

• Hunter bordered (lat. Dolomedes fimbriatus) widespread on the Eurasian continent and occurs along the shores of bodies of water with standing or very slow flowing water. Often settles in marshy meadows, shady forests or gardens with high humidity. The body length of the female edge hunter varies from 14 to 22 mm, the male is smaller and rarely larger than 13 mm. The color of spiders of this species is usually yellowish-brown or almost black, with light yellow or white stripes on the sides of the abdomen.

• Apulian tarantula (lat. Lycosa tarantula)– a species of spider belonging to the family of wolf spiders (lat. Lycosidae). Lives in the open spaces Southern Europe: often found in Italy and Spain, digs burrows half a meter deep in Portugal. The size of the tarantula is impressive - up to 7 cm in length, individuals are usually colored red, less often - brown, with several transverse stripes on the body light color and one longitudinal.

• Spiny orb-weaving spider or "horned spider" (lat. Gasteracantha cancriformis) distributed in the tropics and subtropics, in the southern part of the USA, in Central America, in the Philippines, in Australia. The size of the female is 5-9 mm, the width reaches 10-13 mm. Males are 2-3 mm long. The legs of the spiny spider are short, and there are 6 spines along the edges of the abdomen. The color of the spider is very bright: white, yellow, red, black. On the abdomen there is a pattern of black dots.

• Peacock spider (lat. Maratus volans). This spider comes in all sorts of colors: red, blue, light blue, green, yellow. The coloring of females is paler. An adult reaches a size of 4-5 mm. Males attract females with their beautiful outfit. The peacock spider lives in Australia - in Queensland and New South Wales.

• Smiling spider (lat. Theridion grallator) or a spider with a happy face is completely harmless to humans. This one lives unusual spider on Hawaiian Islands. Its body length is 5 mm. The color of the spider can be varied - pale, yellow, orange, blue. This species feeds on small midges, and the bright color of the individual helps confuse enemies, especially birds.

• Black Widow (lat. Latrodectus mactans)- it is very dangerous and poisonous species spiders Lives in Australia North America, and is also found in Russia. The size of females reaches 1 cm, males are much smaller. The body of the black widow is black, and on the abdomen there is a characteristic red spot in the shape of an hourglass. Males are brown with white stripes. A black widow's bite is deadly.

• Karakurt (lat. Latrodectus tredecimguttatus)- This is a type of deadly poisonous spider from the black widow genus. The female karakurt has a size of 10-20 mm, the male is much smaller and has a size of 4-7 mm. There are 13 red spots on the abdomen of this scary spider. In some varieties, the spots have borders. Some mature individuals are devoid of spots and have a completely black shiny body. The karakurt lives in Kyrgyzstan, in the Astrakhan region, in the countries Central Asia, in the south of Russia, Ukraine, in the Black Sea and Azov regions, in the south of Europe, in North Africa. Karakurt was also seen in Saratov region, Volgograd region, Orenburg region, Kurgan region, in the south of the Urals.

Lifestyle

All arachnids, with the exception of some mites, are carnivores, usually eating insects and other small animals, which they in most cases catch alive. Only the liquid tissues of the prey are sucked out (external digestion), no solid particles are ingested. Most arachnids are armed with venom glands, although only a few are dangerous to humans.

Of the spiders in the United States, the most poisonous species is the “black widow” ( Latrodectus mactans) and those close to him; their bite is very painful and sometimes leads to death. Some large tropical tarantulas are considered dangerous, but the bites of members of this group living in the southern and western United States are generally comparable to the sting of a wasp. Scorpions, of which only a few are highly poisonous, inflict painful stings with a poisonous sting at the end of their tail. Contrary to popular belief, the large nymphs found in the southwestern United States are not venomous. Some ticks carry pathogens, such as Rocky Mountain fever.

Arachnids, like insects, live everywhere. They are common up to 80° N, up to altitude boundary life in the mountains and are even found in the air, thousands of meters above the ground, where they are carried by the wind along with pieces of cobwebs.

Nutrition

The front part of the arachnids' intestine (the pharynx), with strong muscles, acts as a pump. The midgut usually has lateral protrusions, increasing its capacity. Liver secretion and salivary glands arachnids breaks down proteins. It is injected into the body of killed prey and turns its contents into a semi-liquid state, and then such food is absorbed through the pharynx (this method is called extraintestinal digestion).

Spider Reproduction

As spiders grow, from time to time they shed their tight chitinous shell and acquire a new one. They can molt up to 10 times in their entire life. Spiders are dioecious, with the female being much larger than the male. During the mating season, which lasts from mid-autumn to early spring, the male fills the bulbs located at the ends of his pedipalps with sperm and goes in search of a female. After performing the “mating dance” and fertilization, the male spider hastily retreats and dies after some time.

After two and a half months, the female spider lays eggs, and after 35 days small spiderlings appear, living in the web until the first molt. Females reach sexual maturity at 3-5 years of age.

Among spiders, only poisonous ones pose a danger to humans. In the CIS countries there is one such species - the karakurt, or black widow. With a timely injection of a special serum, the bite goes away without consequences.

How do spiders weave webs?

All spiders weave webs. It is used not only for hunting, but also for movement, creating smooth walls in burrows, and building egg sacs. Most spiders have four openings on their abdomen called spinnerets. When a spider releases a web, it appears to consist of a single thread.

In fact, one web consists of many thin threads glued together with a special liquid. Once this liquid enters the air, it hardens. Many spiders use the web thread to climb back into the hole.

Different species of spiders have different webs. It may be sticky, dry, or rubbery. The threads of the web are so strong that some spiders use it to travel many kilometers through the air. Spiders can eat their web if they no longer need it and begin to weave a new one.

Male spiders are smaller in size than females. During mating, males must be very careful. The female may not accept courtship and decide to simply eat her partner. Even if mating has occurred, the female can attack later, so males usually try to retreat faster. But this doesn't happen too often.

Spiders lay from 2 to 1000 eggs depending on the species. Almost all females spin a web and place the eggs in a "blanket", then hang the sacs somewhere safe and guard it. When the little spiders hatch, they often stay inside the sac to grow a little more. Some females immediately leave the egg sacs unattended and do not monitor them.

What is arachnophobia?

Arachnophobia, which is the name given to the fear of arachnids, is a completely new disease, manifests itself as special case isectophobia (fear of insects in general). Since ancient times, man has experienced fear of the unknown, of something unlike him. A certain fear of insects is inherent in every person on an instinctive level. We are all initially afraid of what seems to us unidentified and unexplored. Someone, having learned more about spiders, ceases to be afraid of them, realizing the harmlessness of most species. And some people remain with their insectophobia for a long time; spiders begin to seem like something that poses a huge danger and threat.

Arachnophobia is very common, affecting almost half of all women and a fifth of all men. Scientists suggest that fear of spiders is so common in women because they are more sensitive to tactile sensations and have more sensitive skin. The sensation of being touched by an insect leaves a greater impression on them, which plays into their fears.

Arachnophobia is often combined in a person with other fears:

• myrmecophobia – fear of ants;
• blattophobia – fear of cockroaches;
• Lepidopterophobia – fear of butterflies.

All these fears have the same root causes; often they are not separated, but are generalized into one disease - insectophobia (fear of insects is also called entomophobia).

Causes of phobia

Arachnophobia is a disease that is very common in modern world. This is due to big amount city ​​residents. This part of the population rarely comes into contact with spiders, which is why it is not always possible to distinguish a dangerous species from a harmless one.

The practical significance of spiders when modern level our knowledge about them actually comes down to the harm caused poisonous bites some forms. However, many spiders are undoubtedly useful as exterminators of harmful insects, but this role has not yet been accurately assessed. There are also some prospects for the technical use of spiders.

The biological significance of spider venom is mainly to kill prey, so the venom is usually toxic to insects. There are few species of spiders whose venom has a strong effect on warm-blooded animals, but among them there are some that are extremely dangerous for humans and domestic animals. According to the nature of the poisoning caused poisonous spiders are different. The venom of some causes mainly local necrotic reactions, that is, necrosis and destruction of the skin and deeper tissues in the bite area. The poison of others has strong effect throughout the body, in particular the nervous system.

The death of people and domestic animals bitten by some large tropical tarantulas has been noted more than once, but the poisonousness of most of these spiders has not been precisely determined. Among them, Phormic-topus has poison in its venom glands that is sufficient to kill 20 mice. It is known that the Bushmen in South Africa They used the venom of spiders from this genus, mixed with the juice of amaryllis bulbs, to poison arrows.

The venom of the spider Mastophora gasteracanthoi-des (family Araneidae), found in Peru, has a strong necrotic effect, where it infects people involved in caring for vineyards. The bitten person feels a sharp pain, then appears severe swelling and further tissue destruction occurs in the affected area, so that internal organs may be exposed. Death, noted in a number of cases, probably occurred from secondary wound infection. A similar picture is caused by the bite of the Brazilian Lycosa gar-toria (family Lycosidae).

The general effect on the body is characteristic of the venom of the Brazilian Ctenus nigrivent-ris (family Ctenidae), whose bites are dangerous. Even more dangerous is the small (4–5 mm) racer Dendjyphantes noxiosus, found in Bolivia. Its bite causes inflammation and severe pain, as if from a hot iron; Blood appears in the urine, and death occurs within a few hours.

The venom of spiders of the genus Latrodectus (family Theridiidae), which includes the karakurt (L. tredecimguttatus), found in our desert and steppe zone in Central Asia, the Caucasus, Crimea and also common in Iran, Afghanistan and along the coasts Mediterranean Sea. In America, an equally poisonous species of the same genus is widespread - L. mactans, which there received the name “black widow”. Other species are found in tropical countries.

The most terrible spiders in the world

Yellow (Golden) Sak

The main habitat is Europe. Do not grow more than 1 cm in volume. The color is golden, translucent. Yellow Sak can crawl around in a residential building for quite a long time, while remaining unnoticed, because its nondescript appearance and small dimensions allow this. IN natural conditions he always builds himself a house that looks like a pipe bag. Necrotic wound causing severe pain, is protected from the bite of this animal. These symptoms are very similar to the effects of violin spider venom. Saki are prone to self-defense; they attack only when they feel in danger.

Wandering Brazilian spider

It was no coincidence that this nickname was given– constantly change their location in search of prey. These spiders live mainly in South America. This species is considered one of the most dangerous. The wanderers already have quite impressive volumes - about 10 cm. The amount of poison contained in one individual is enough to kill 225 mice. An antidote to it already exists. But its bite, one way or another, will lead the human body to a severe allergic reaction.

The Wanderer is difficult to notice in nature due to its discreet sandy coloring. As funny as it may sound, it is usually found in baskets of bananas, which is why it got the nickname “banana”. The wanderer chooses prey that is an order of magnitude larger than its own size - these can be birds, lizards, or even other arachnids.

Brown recluse (violin)

This type represents very great danger for humans, since after a bite the poison disperses throughout the body in just one day. If the victim is not hospitalized in time, the outcome will be very disastrous. This spider, like the Yellow Sac, will not attack first unless it feels a threat to itself, but in any case, contact with it should be avoided.

Hermits grow to a maximum of 2 cm, and usually hide in dry and dark places. They can be found in California and other US states. This species can be distinguished by its characteristic shaggy “antennae”; they also have only 3 pairs of eyes, unlike most spiders, which have 4 pairs, i.e. 8 eyes.

Black Widow

As mentioned earlier, the most dangerous spider on earth is female black widow. Its poison is deadly. In size, like the hermit, it can reach a maximum of 2 cm. It is easy to recognize: black, with small spots on the back. And a widow, because after mating she takes the life of her partner. By comparison, poison rattlesnake 15 times less more dangerous than poison this terrible arthropod. The female's bite is so dangerous that if the victim is not injected within half a minute, death may well occur. Black widows are not limited to one country; they can be found in deserts all over the globe.

Tarantula (Tarantula)

Found in desert and steppe areas where they dig deep holes for themselves. Nature has endowed this species with a unique beauty. His body is colored gray, brown, orange colors. Sometimes striped individuals are found. Unlike hermits, tarantulas are completely furry. They usually grow up to 3-4 cm. It has a second name - tarantula, as it feeds on small birds. They hunt at night thanks to their excellent night vision.

Water spiders

Their usual home is ponds in North Asia and Europe. They do not grow more than 1.7 cm. They swim very well, which is why they have this name. They live underwater, where they weave their nets in the algae. They eat a variety of small aquatic life. Its poison is absolutely not dangerous for humans, but it looks scary.

Crab spider

There are over 3 thousand species in the world. They are large in size and have a wide variety of colors, which, oddly enough, are similar to their habitat. They are like chameleons and can blend into almost any surface, be it greenery or sandy terrain.

Rooted in three places:

• Southern Europe
• North America

Crab spiders do not pose a strong threat to people, but they are often mistaken for poisonous hermits, so they are truly feared no less than others dangerous species. They were named after crabs, as they are similar in appearance and very mobile, like these decapod crustaceans. Like brazilian spiders, they do not weave webs, but prefer to hunt. I can only move backwards and to the sides.

Wall tegenaria

Quite a rare species today, however, the most close-up view in Europe. Its dimensions range from 12.5 to 16 cm in straightened limbs.

The abode of this spider is as follows:

• Uruguay
• North Africa
• central Asia

You can accidentally stumble upon tegenaria in caves or old buildings. In England, this spider was called “cardinal”: according to legend, the once-living Cardinal Wolsey, seeing this spider, experienced a very strong fright. Tegenaria move very quickly. The structure of their web is very thick, so the caught insects have practically no chance of escape.

Cerbal Arabian

It was first found at the end of 2010 in Israel. It can be found in sand dunes. It has a large, silver-gray body with distinctive stripes on its legs. The coloring is quite scary. To date, little is known about their lifestyle. According to scientists, they are especially active during the hottest time of the year.

Giant baboon spider

Has a second name – Red Cameroon. The length of the body is 10 cm, and the legs are approximately 20 cm, which in general gives the spider a size of as much as 30 cm. The baboon spider belongs to the tarantula family and loves subtropical forests.

Quite a few colors predominate in color:

• orange
• grey
• brown
• black

Its legs, unlike its body, are covered with small hairs. The diet is quite large, it can feed on insects, but will not refuse mice and other similar living creatures. It injects a killing poison into its prey.

Of all the above, the title of the most deadly dangerous spider on earth was appropriated by the Black Widow. The title of the most terrible, without a doubt, belongs to the wandering Brazilian spider.

Quantity known to science only affects spiders modern species There are about 42 thousand, plus more than a thousand fossil arachnids. Distributed everywhere, living not only on land, but also in water, predators and, with rare exceptions, vegetarians, harmless and deadly to humans, living on earth for over 100 million years, spiders are also interesting because they, like few insects , have a unique external structure. First of all, this concerns the organs of vision. Therefore, the question of how many eyes a spider has is interesting.

Number of eyes in spiders

Zoo-ophthalmologists (experts in the field of animal vision), when asked how many eyes a spider has, will not give a definite answer. The fact is that the number of eyes in spiders varies depending on the species.

But it is still known how many eyes most species of spiders have - four pairs. However, the owners of 12 (!) organs of vision are known. During evolution, nature left spiders with as many visual organs and exactly as much strength as they needed for survival and reproduction. At opposite poles in terms of visual power are cave spiders - practically blind - and jumping spiders, whose visual power is equivalent to that of a human and at the same time they are still capable, as has been proven, of distinguishing colors.

Types of eyes

The eyes, usually located in two rows, have different functionality. The so-called medial, also known as the front pair, are called the main eyes. All other organs of vision are called collateral. Unlike insects that have so-called compound eyes, where individual sections of the eyes perform functions unique to them, in spiders the role of such facets is played by separate eyes. An example is side eyes, the main task of which is to warn their owner of approaching danger.

The power of vision

The main eyes of spiders are able to see even what a person cannot distinguish. In particular, the sensitivity of these creatures to ultraviolet radiation has been proven. Almost 6 thousand species of jumping spiders have this ability, which, unlike other representatives of arachnids, prefer not to wait for prey in an ambush, but, on the contrary, to actively hunt it.

Web spiders, spiders that catch prey using webs, have poor eyesight. Their vision allows them to record the movement of relatively large objects (moths, flies) and respond to changes in the direction and intensity of light.

Features of the eyes

Scientists have determined that regardless of how many eyes a spider has (cross spider, crab spider, sand spider or another type of these invertebrates), all eyes function as a single organ. First, the presence of a potential prey (fly) is determined by the rear or lateral eyes. This happens at a distance between the spider and the fly, which is at least 20-25 cm. Next, the main eyes come into play, to which the main focus is transferred. It is they who determine that in front of the spider is the desired object of hunting, and not a foreign object.

Thus, the answer to the question, how many eyes does a spider have, requires counter clarifying questions - which spider and living in which habitat? Only after determining these parameters can an accurate answer to the question be given.

The main phobia of many people is the fear of spiders. But these defenseless creatures do not cause any harm to humanity, and occasionally they can attack in defense. Only a few species in the world are capable of causing harm to humans.

Variety of spiders

As for species, there are about 40 thousand of these representatives of the arachnid class. And each of them is unique. And this is not the limit, since each species has its own subspecies, and the number of all arachnids can exceed a six-digit number.

Sensory organs

The spider's main sensory organ is its eyes. Depending on the species, the spider has its own pair of eyes, ranging from one to eight. Basically, many species have eight pupils, but there are also those that feel great with a pair of eyes, like common insects. As an example, the tarantula spider has four pairs, the cross spider has the same number, and the tarantula also does not differ in the number of eyes. Oddly enough, spiders have very excellent vision and can compete with their sharpness even with humans. The exception is those species that spend their entire lives in the dark; they do not need to have good eyesight. They are more guided by their paws, which have very sensitive hairs. This small detail is very important for the spider, since these hairs replace them with:

• ears (with the help of them they are even able to hear the direction of the wind, not to mention any sound);
• tongue (spiders don’t care how much tasty food, it is important to them whether it is edible or not, and it is this function that the hairs perform);
• nose (the sense of smell also lies on the feet).

After conducting many experiments, scientists came to the conclusion that some types of spiders are able to distinguish colors, which is not given even to dogs. The experiment consisted of the fact that the spider was asked to choose one fly between two areas of illumination: green and red, which was accompanied by electric shock. In repeated situations, the predator chose the fly under the green light.
Each individual has both main and lateral eyes. Each pair of them has a viewing circle of approximately 40%. Some types of spiders (for example, tarantulas) have a viewing angle of 360 degrees. If the spider noticed the prey with its side eyes, then before attacking, it will turn to it with its main gaze.
As they say, “there are no eyes in the back of the head,” but this is by no means about our main characters. It doesn’t matter whether a spider has two, eight or sixteen eyes, in any case it will remain the same fearless, brave and courageous predator on Earth.