What are the structural features and behavior of the cross spider? Features of the cross spider. Research project "biological forms of behavior of the orb-weaving spider" What is the complex behavior of spiders based on?

Spiders are a special class of living creatures, which were named after a girl from Greek mythology. The myth about a weaver named Arachne, who dared to challenge Athena to a skill competition, says that the goddess won without recognizing the efforts of a simple girl. Out of resentment and frustration, Arachne wanted to hang herself. However, by Athena she was turned into a spider, tirelessly weaving her web.

Now let’s take a closer look at some of the characteristics of these arthropods. What features of the structure and behavior of the cross spider help these living creatures survive?

The special life of spiders

The cross spider (photo confirms) is a typical representative of its class. To the squad

Arachnids also include ticks and scorpions. More than 300,000 species of representatives of this class live in tropical and mixed forests of our planet. To find out what features of the structure and behavior of the cross spider exist, you need to be a very careful observer. Most often, the “weaver” himself is invisible to us. But its web is quite noticeable!

The behavior of the cross spider is determined by its lifestyle and habitat. Forests, parks, gardens and various green spaces - all this can be a home for representatives of this species. Araneus diadematus can also be found quite often in human homes.

cross spider

The bodies of all spiders are similar:

• small cephalothorax;
• large, egg-shaped abdomen;
• 8 legs.

This species got its name from the pattern on the surface of the back, similar to a cross. The so-called eyes (8 pairs) are located in the front part of the spider’s cephalothorax. The mouth of the cross consists of several “parts”: a pair of jaw-claws with poisonous glands at the base, as well as claws (chelicerae) - organs of touch.

The structural features of the cross spider allow it to survive, attack and feed with the help of its powerful jaws. On the legs there are comb-shaped claws, with which the “forest weaver” creates its sticky network. Spider warts are located at the bottom of the abdomen. Despite having so many eyes, the spider family sees very poorly. The main aid for survival is the sense of touch with the help of sensitive legs.

Method of feeding the cross

A builder and hunter, the cross spider feeds on everything that falls into its traps. These could be horseflies and flies, mosquitoes or various midges and small insects. All representatives of this species are predators, including the cross. The photo helps to see the process of catching insects in a sticky web. Grabbing prey with its legs and hooked jaws, the spider bites through it, injecting paralyzing poison into the victim's wound. At the same time, digestive juice enters its body, softening the insides of the fly.

With his insatiable appetite, this insect hunter is capable of sucking out more than a dozen flies at a time. If there are too many victims, behavioral characteristics The cross spider tells him to wrap the captives in a cocoon and leave them “for later.” The supplies are suspended from the trap on threads. Spiders are not adapted to eating solid food. But they can suck out the softened insides of insects. For this extraintestinal method of feeding, arachnids do not need stomachs.

How do spiders reproduce?

Only towards the end summer period Eight-legged forest dwellers reach puberty. Observing what features of the structure and behavior of the cross spider contribute to the reproduction of this species, biologists found that females are more than twice as large as males. Living alone, only in the fall the spider sets out to look for a “lady”. By attaching his thread to the female’s trap and pulling it, he attracts the female’s attention in this way. The mating that occurs becomes the last event in the life of this male - the “lady” eats him after the fertilization process. Instinct of satiation, nothing personal!

The female spider lays eggs in autumn months, wrapping the masonry in a thick thread cocoon. With such silk protection, future offspring will easily survive any frost. Suspended in secluded places, in crevices of tree bark, these cocoons will open next spring. Small spiders, having overwintered, will come out to build their traps.

What makes a spider weave a web?

Without its elegant trap, this predator would not be a spider. Let's look at what features of the structure and behavior of the cross spider make it weave webs for life and nutrition.

• Hunger is the root cause of all actions of representatives of this species. To have food, you need to find a place suitable for a trap.
• When the arthropod decides on the territory, the next instinct turns on - the cobweb composition begins to stand out.
• Each action causes subsequent signals about the necessary continuation. Everything is arranged simply and clearly.

Spider weaving skills catcher net may be congenital, built-in or acquired, depending on the environment of residence. However general scheme a web always has many identical parts. Ideally woven spiral turns are fixed along the radii of the network with equal angles. In this case, the center of gravity always coincides with the center of the spider web.

About spiders, webs and humans

Remembering signs and Scientific research, you can find out what features of the behavior and structure of the cross spider have been used by humanity to treat various diseases.

• By applying the removed fresh spider web to a small wound, you can stop the bleeding.
• Decoration with the image of a forest octopus is believed to bring monetary luck.
• European healers of the Middle Ages claimed that wearing a pendant in the form of a spider on the chest would protect against diseases.
• If the “handsome guy” sits in the very center of his trap and does not crawl out, then it will definitely rain.
• If spiders weave fresh webs, it means sunny weather.

In conclusion about the benefits of the arachnid order

If it were not for this family, humanity could annually suffer great losses from
crop losses. Spiders play almost the leading role in the fight against insect pests. During a season, on a hectare of forest territory, these gluttons destroy more than 200 kg of possible carriers of various infectious diseases.

Vivat to the cross spiders!

Flexible, have several options. The cross spider builds a web using its body as a plumb line, that is, by pulling the threads of the web frame, it uses the force of gravity of the Earth. What happens if you put it in zero gravity? Such an experiment was carried out on a satellite and it turned out that after several unsuccessful attempts the spider used a backup program - not to descend while hanging on a thread, but to run around the walls, releasing the thread and only then pulling it.

Spiders live next to us, and anyone can do many interesting experiments with them - if only they could use their imagination. Another example: spiders were fed medications that affect a person’s mood and performance. Under the influence of one medicine (which makes us impatient), the spider built a web somehow, with holes; under the influence of another (concentrating attention) he built a magnificent, geometrically perfect structure. And under the influence of the drug, he created delusional abstract structures instead of cobwebs. This means that it is not enough to have a program; it is also important what state the nervous system is in. Uncertainty, fear and others emotional states, are characteristic of all highly organized animals, as well as humans.

Motivations for spider behavior

For a program to be retrieved from the program repository, a change must occur internal state organism. In order for an animal to go looking for food, it needs to feel hungry. Hunger is an internal motivation for eating behavior.

When a male spider's gonads mature, the hormone they secrete into the blood enters the nervous system, and acts as motivation to start a female search program. The male leaves his web and goes to look for the female. But how can you recognize her? After all, he had never seen spiders. For this case, the characteristic features of the female are encoded in the program. Now all the male’s senses are aimed at detecting something similar in the world around him.

Let's say the code is: "look for a rounded movable object with a cross." Then the brain will react to anything that fits this code, including an ambulance. If the code is written so that none natural object, except for the female, did not fit him, the male recognizes the female. About the same in terms of unique and characteristic features The computer program recognizes the letters in the text, no matter what font it is typed in. And just as we can deceive a computer by drawing only their signs instead of letters, so we can deceive a spider by showing it instead of a female dark cardboard figures that somehow resemble her. If their signs coincide with the code, the male starts a program for demonstrating mating behavior.

Signal stimuli

The characteristics of an object (and the object itself is their carrier), which coincide with the program code, are called signal stimuli by ethologists. They act like a key that unlocks your door (this instinctive program) and does not unlock the doors of your neighbors (other instinctive programs).

A complex instinctive act is a chain of sequential actions launched in response to signal stimuli. Such incentives can be not only the partner’s behavior, but also the result of one’s own previous actions.

For example, the coincidence of the features of the resulting web frame with the encoded features of the frame acts as a signal stimulus that triggers the next series of actions—the application of a spiral layer of threads to the frame. The instinctive program is read, constantly checking with the information brought by the senses.

Questions about this material:

Spiders... What we know about spiders is that they cause fear in many, and spiders cause a feeling of disgust in many. On our website you will get acquainted with some types of spiders. We will tell you about what types of spiders there are and what makes them remarkable. In addition, we will dispel some myths that in our minds are quite strongly associated with spiders. Also, we will give you some useful tips regarding how you can get rid of spiders in your garden or home.

Spiders were among the earliest animals to live on earth. Despite the fact that the age of life of spiders on the planet is quite significant, spider fossils are quite rare. According to historians, biologists and archaeologists, the first spiders on our planet appeared approximately four hundred million years ago. The ancestors of modern spiders were an arachnid insect, quite thick, large sizes. This arachnid insect lived in water for quite a long period of time. The first ancestors, who were already similar in their body structure and other characteristics to modern spiders, were Attercopus fimbriungus. Fossils of Attercopus fimbriungus (Attercopus fimbriungus) have been found by archaeologists, although, as we said above, the number of such finds is quite small. Attercopus fimbriungus lived approximately three hundred and eighty million years ago, that is, approximately one hundred and fifty million years ago before the first dinosaurs appeared on the planet. Most of the early spiders, the so-called segmented spiders, that is, those that already had a fairly well-formed abdomen, belonged to the Mesothelae variety. The Mesothelae group was distinguished by the fact that the place from which they unwound their webs was in the middle of their abdomen, and not at the end of the abdomen, like their modern “relatives”. It is quite likely to assume that such distant ancestors of spiders lived on the ground, they were predators, and lived in giant thickets and fern forests. These spiders lived approximately in the middle of the Paleozoic. Apparently Mesothelae were predators and hunted other primitive insects such as cockroaches, roofers and centipedes. The web may have been used simply as a protective covering for the eggs; later, it is quite possible that the web was also used to create simple nets built on the ground, as well as to create a so-called hatch or trapdoor. Thanks to the development of evolution, including the evolution of plants, the life of spiders began to change. Spiders with a web-weaving device at the end of their abdomen, and these spiders were called Opisthothelae, appeared more than two hundred and fifty million years ago. These spiders could already weave more complex networks, which were real labyrinths. Thus, such complicated nets caught smaller insects directly on the ground, and nets could also be found in foliage. With the coming Jurassic period(approximately one hundred and ninety-one - one hundred and thirty-six million years ago), during this historical period dinosaurs were already walking on our planet, aerial networks that were skillfully woven by spiders were already designed to lure into a trap and, accordingly, catch, that incredible number of insects that simply swarmed in the foliage. Approximately the same with increasing total number spiders on the planet, the spiders themselves became quite easy prey, thus the spiders were forced to adapt to the new habitat. Today there are enough mine fossils that are dated to the Tertiary period. According to analysis of fossil data, spiders can be seen seemingly trapped in tree resin. So, according to these fossils, the species diversity of spiders that we can observe now is quite consistent species diversity these insects, which existed approximately thirty million years ago.

Most spiders are small, featureless arthropods that are harmless to humans. Their beneficial role in preserving insect populations far outweighs the danger from the few spiders that sometimes bite people. Only a few species of spiders are poisonous; spiders and insects are engaged in a fairly serious struggle, in which the advantage is often on the side of predators.

Tarantulas, jumping spiders, and some other species frighten people, who mistakenly believe that they pose a serious danger. Although these spiders are large, hairy, and unimpressive-looking, their bite is generally less dangerous than a bee sting. However, if you are allergic to spider venom, any spider bite will cause you to have a serious reaction. Many people are afraid of spiders, but knowing how to distinguish harmless animals from truly dangerous ones, how to prevent them from entering your home, and how to protect yourself from those that can actually cause harm, you can save yourself from panic fear, or at least reduce it.

The main product that spiders feed on is insects, but large varieties can also attack small birds and animals.

Are recluse spiders the most dangerous?

Although only a few recluses are truly venomous to humans, it is best to consider the entire species as potentially dangerous.

A small digression: we must not forget that spiders are not insects; their structure is closer to crabs and crayfish. Hermit spiders choose garages, woodpiles, basements, etc. as their habitat, often settling near and inside human dwellings. They are most active at night (like many spiders); insects at home also wake up then, and eight-legged creatures begin hunting them. They often bite people in their sleep, most likely when a person accidentally brushes against them, causing a reasonable self-defense reaction. Others get bitten when they take clothes that for a long time hung untouched in the closet, and in which hermits settled.

Poisonous spiders

In fact poisonous spiders do not pose as great a threat as is commonly believed. The existing antivenom for bites of various types of spiders is now very effective, and deaths from bites are very rare; for example, in the USA, an average of 4 people die per year. However, spider venom can cause severe skin lesions that require immediate treatment and long aftercare procedures. All spiders use venom to kill their victims after they are caught in webs or captured by spiders through other means. Poisonous spiders have a more serious poison, aimed at immobilizing and killing large victims, and they use it not only for food, but also for self-defense. The likelihood of death or serious injury from a bite is very low - however, in any case, it is better to consult a doctor to avoid serious consequences.

Tarantula spiders

Tarantula spiders have long taken their place as pets among breeders who love extreme sports. An attractive person helps them with this. appearance, variegated color, low requirements for nutrition and care, etc. They are recommended for those who want to have a spider at home for the first time. They are also fairly long-lived pets, with an average life expectancy of a couple of decades (for the fairer sex). Tarantula spiders are tropical inhabitants that have now gained popularity in our country as pets. As the name implies, tarantula spiders, at least some of their varieties, feed not just on insects, but also on birds. Of course, tarantulas believe, like other spiders, that insects are quite acceptable food for them, but they need a lot more of it. Tarantula spiders are large creatures with powerful mandibles and strong poison; their method of hunting can be called active, since they do not wait for the animal to become entangled in a web, but attack it from ambush.

House spiders

Several species of spiders are commonly found in households. With rare exceptions, they are quite harmless, being in corners and building networks there, some of them are even beneficial because they feed on household pests (flies, moths). Sometimes house spiders bite people, but in most cases their bites are not dangerous. But, if your house spiders are black widows, recluses, and other varieties that are deadly, you need to get rid of such a terrible neighborhood.

What can you do about this?

To keep spiders out of your home, you can use mechanical methods - killing them with your hands, a newspaper, a broom, or sucking them out with a vacuum cleaner. House spiders are also afraid of chemical sprays based on boric acid, chlorpyrifos, etc. If you seal cracks in your house, increase the sealing of windows, and remove garbage near your house, house spiders are unlikely to get to you. For prevention, you can also use special sprays designed for spraying outdoors. If you have been bitten by a spider and you do not know what type it is, it is better to visit an infectious disease doctor.

Dream Interpretation: spiders

Arachnophobia, the fear of spiders, is the most famous phobia among Americans, and quite common among us. Many people say that these hairy eight-legged creatures disgust them. If you look in the dream book, spiders dream of many situations awaiting you in the future, but why do they appear in your dreams? Most likely, this is an expression of your subconscious attitude towards them, but the image of a spider is much deeper than just the feeling of goosebumps from its appearance. If you've ever read one of the African tales, you may have noticed that spiders are cunning, cunning creatures often associated with deception. This is most likely caused by their diet. Very often, having seen a dream, we take a dream book; spiders in it (in various interpretations) are precisely a warning about the danger of falling into the web of deception. Another association associated with spiders comes from their ability to spin beautiful, complex webs. The famous myth about Arachne turning into a spider also testifies to this. If you see a web in your dream, it may well mean that your creative impulses are being ignored; spiders spinning webs indicate that inspiration is right in front of you. When considering the symbolic meaning of spiders, one must not lose sight of the cannibalistic tendencies of many females, who kill their partners after mating. We can say, without looking at the dream book, that spiders represent the feminine energy within us, and if you have dreams about a spider killing your partner, it means that serious changes are coming in your life. Spiders, unlike insects, do not have antennae (antennae) or jaws. The body is covered with an external skeleton (exoskeleton) and consists of two sections - the cephalothorax, formed by the fused head and chest, and the abdomen. At the anterior end of the cephalothorax there are simple eyes, the location of which serves as an important classification feature. Most spiders have four pairs. The cephalothorax bears six pairs of limbs. At the front of the head are two downward, jaw-like chelicerae, each of which ends in a sharp claw. It opens the poisonous glands located in these limbs. The second pair are pedipalps, used as palps and grasping structures. In mature males, their ends are modified and are used for mating. Between the bases of the pedipalps there is a small mouth opening. All spiders, unlike insects, have four rather than three pairs of walking legs. The last segment of each of them bears at least two claws, and in some species there are many more. The arachnoid glands open on the underside of the abdomen, usually with six arachnoid warts. In front of them are small respiratory openings - spiracles, or stigmas. On the abdomen are modified organs, spinnerets, used in spinning silk. The breathing holes on the abdomen lead to what are called book lungs (named for their layered structure) or a system of air plugs (tracheas).

Digestive system spiders are adapted exclusively to digesting liquid food, so insects capture their prey and then suck the liquid out of them. Spiders have quite complex brains, larger or smaller in certain parts, depending on whether the animal locates prey primarily through contact or vision. With a bite, spiders paralyze their prey: this is how their venom acts on the victim’s nervous system. They can only feed on liquid food, since the spiders' mouth opening (in the form of a tube) is very narrow. Therefore, spiders inject a special substance into their prey, which acts like digestive juice, corroding tissue. They then suck out the victim, leaving only an empty skin. This type of digestion is called extraintestinal. All spiders are by nature carnivorous insects, and most of them live only thanks to mining. They can survive for long periods of time without food. Some spiders have been able to stay alive for two years without feeding. Spiders hunt both day and night. All are well equipped with sensory hairs on their bodies and legs, they can easily detect the slightest change in air currents, indicating the movement of prey. Spiders will often feed on other spiders. Most hunters will attack prey that is smaller than themselves and will run away from prey that is larger than them. Those that have well developed jaws (chelicerae) tear apart prey and drink digestive juices from it. Those whose chelicerae are not very developed inject poison and then suck out the juice. The feeding process is slow; for a large fly spider it can take up to 12 hours. Since the soft cuticle of the spider's abdomen stretches when it absorbs food, but when it reaches maximum quantity further stretching of the liquid is impossible. None of the harder sclerotized parts are capable of increasing in size because, as in all insects, the skeleton is on the outside. So the old spider must moult. The old cuticle splits and makes room for a softer one, which strengthens over time. Nymphs molt frequently, every few days, during which time their size increases; this does not happen with mature spiders. The interval between molts increases as the spider ages. Smaller species shed about five times less than big spiders. Sometimes the shedding doesn't happen as planned, the legs get stuck, etc. The spider then dies, or it may break its legs to release them, they are very susceptible at this stage.

The complex behavior of spiders - their "industry", that is, the construction of trapping nets, flight devices, underground or underwater dwellings, as well as the "care of offspring" developed in many species - may seem to be a manifestation of intelligent activity of the same order as conscious activity person.

However, a study of the way of life of spiders clearly shows that the basis of their psychological activity turn out to be more or less complex instincts, that is, certain norms of behavior characteristic of each individual species that are not acquired personal experience, but constitute a species characteristic of a given animal.

Like everyone else species characteristics- a certain body shape, the location of the eyes, a pattern on the surface of the abdomen, etc. - instincts are inherited from generation to generation and immediately, already in finished form, appear at the appropriate age or at the appropriate stage of development.

So, for example, newborn cross cubs, emerging from the egg cocoon only the next spring, that is, several months after the death of their parents, stay together in this cocoon, but in case of danger they scatter in different directions - “scatter like beads.”

This behavior of theirs turns out to be very expedient: if it is impossible, as the proverb says, to chase two birds with one stone at once, then it is even more difficult to chase at one time a hundred spiderlings scattering in all directions. But now the danger has passed, and the tiny spiderlings again gather under the shelter of the silky cocoon arranged by their mother, which protects them well from rain and dew.

The cubs of wandering spiders - tarantulas and smaller forms of eight-legged "wolves" - behave completely differently. In these species, females “carefully” carry their egg cocoon with them, and when the eggs hatch, the cubs begin to crawl over the mother’s body or leisurely wander around her.

However, at the slightest alarm, the spiderlings instantly gather in a tight pile on the mother’s body, which can really protect them from attacks.

But days go by, and the close “friendship” between brothers and sisters disappears: the grown-up predators scatter apart and, when they meet, treat each other as possible prey. This new instinct also turns out to be very expedient, since it can be difficult for several predators to feed in one place and each of them occupies a separate hunting area for itself.

Young web spiders begin to weave nets, and at the same time it turns out that they, having never seen how their parents did it, immediately “know how” to build them, and, moreover, exactly in the way that is typical for this type of spider: crosses - in the form a vertically stretched network, spiders of the genus Linithia - in the form of a horizontally located arch. Nobody teaches the silverback spider how to build its underwater bell and carry air into it, and so on.

We should not be surprised that these hereditary norms of behavior turn out to be well suited to the living environment of the animal: as a result of the constant action of selection, animals that do not satisfy the “requirements” of the environment in their bodily characteristics or in their inherent instincts are inevitably subject to destruction.

Even actions such as bizarre poses and “dances” that precede mating in spiders at first glance are explained by the fact that spiders lack a sense of smell and can only see clearly at close range: therefore, visual signals remain almost the only way for them to in order to be noticed by individuals of the other sex without being mistaken for approaching prey.

Those spiders in which the hereditary instinct of “mating games” or “dancing” did not manifest themselves at the appropriate moment would either remain unfertilized or would be eaten, like an insect carelessly approaching, that is, in both cases they would be left without offspring.

Consequently, despite the external similarity of the behavior of spiders with manifestations of intelligent activity, we have no right to “humanize” their actions or attach any moral assessment to them. The behavior of a female tarantula should not seem to us an incomprehensible contradiction, which after mating often “cannibalically” eats the male who has not managed to escape, and then turns out to be an extremely “gentle” mother, “carefully” carrying her egg cocoon with her everywhere, and after hatching the spiderlings are just as “ carefully" protecting her numerous offspring.

The fact is that in spiders, the life of a male after he has performed his sexual function is no longer valuable for the preservation of the species, and in females, after mating, their usual instinct towards crawling prey comes into force. As for the maternal “concern for the offspring,” then, if the corresponding instinct had not manifested itself in the female at the appropriate time of life, her small, weak and defenseless offspring would have been doomed to death, and, consequently, any deviation from this useful (in the data conditions!) for species life, norms of behavior are invariably swept away by the action of natural selection.

Subphylum Chelicerata

The body of the chelicerates consists of a cephalothorax, from which six pairs of appendages extend: chelicerae designed for fixing food, pedipalps , serving for touch, chewing food, and also as a copulatory organ and four pairs of walking legs. Representatives of the subtype have been known since the Cambrian (terrestrial forms - since the Devonian) and are united in four classes: Horseshoe crabs, Cancerscorpions, Sea spiders and Arachnids.

Class Arachnida (Arachnida)

Arachnids are the most prosperous group of chelicerate animals, numbering 60,000 species. This includes spiders, scorpios And false scorpions, salpugi, haymakers, ticks and other animals. The science that studies arachnids is called arachnology (from Greek Arachne- spider; that was the name, according to one of the myths, of the weaver who was turned into a spider by the angry Athena).

Representatives of arachnids are eight-legged land arthropods whose bodies are divided into cephalothorax And abdomen , connected by a thin constriction or merged. Arachnids do not have antennae. On the cephalothorax there are six pairs of limbs - chelicerae, tentacles and four pairs of walking legs. There are no legs on the abdomen. Their respiratory organs are lungs And trachea . Arachnids have simple eyes. Arachnids are dioecious animals.

The body length of various representatives of this class is from 0.1 mm to 17 cm. They are widespread in to the globe. Most of them are terrestrial animals. Among ticks and spiders there are secondary aquatic forms.

External structure and lifestyle of spiders

Cross spiders (so named for the cross-shaped pattern on the dorsal side of the body) can be found in the forest, garden, park, and on the window frames of suburban and village houses. Most of the time the spider sits in the center of its trapping net made of adhesive thread - cobwebs .

The spider's body consists of two sections: a small elongated cephalothorax and a larger spherical abdomen. The abdomen is separated from the cephalothorax by a narrow constriction . At the anterior end of the cephalothorax there are four pairs of eyes at the top, and hook-shaped hard jaws at the bottom - chelicerae . With them the spider grabs its prey. There is a canal inside the chelicerae. Through it, poison from the poisonous glands located at the base of the chelicerae enters the victim’s body. Next to the chelicerae there are short organs of touch covered with sensitive hairs - claws (pedipalps) . Four pairs walking legs located on the sides of the cephalothorax. The body is covered with light, durable and quite elastic chitinous cuticle . Like crayfish, spiders periodically molt, shedding their chitinous cover. At this time they grow.

At the lower end of the abdomen there are three pairs spider warts , producing cobwebs, are modified abdominal legs.

Construction of a trap network

The most beautiful, wheel-shaped nets (catching nets) are built by female orb-weaving spiders from the family of cross spiders. First, the spider climbs to a high place, usually near an open space (path), and secretes a very light thread, which is picked up by the breeze and, accidentally touching a neighboring branch or other support, is braided around it. The spider moves along this thread to a new point, strengthening the web along the way with an additional secretion. In a similar way, two or three more threads are laid, making up a closed frame, inside which the network itself will be located. Then radius threads are stretched, connecting in the center. After this, starting from the center, the spider moves towards the periphery in a spiral. The spiral thread of the web is covered with droplets of sticky secretion. A signal thread stretches from the web to the spider. The female waits for the signal thread to begin to vibrate. Then the spider rushes at the prey, bites, injects poison with its upper jaws and leaves, waiting.

Internal structure of the cross spider

In a spider, like in other crustaceans, the body cavity is of a mixed nature - during development it arises when the primary and secondary cavities bodies.

Digestive system. The cross spider cannot feed on solid food. Having caught prey, for example some insect, with the help of a web, he kills it poison and lets you into his body digestive juices . After some time, the contents of the captured insect liquefy and the spider sucks it out. All that remains of the victim is an empty chitinous shell. This method of digestion is called extraintestinal .

The spider's digestive system consists of the mouth, pharynx, esophagus, stomach, and intestines. In the midgut, long blind processes increase its volume and absorption surface. Undigested residues are expelled through the anus.

Respiratory system. The spider's respiratory organs are the lungs and trachea. Lungs or pulmonary sacs are located below the abdomen, in the front part. These lungs developed from the gills of the distant ancestors of spiders that lived in water. The cross spider has two pairs of non-branching trachea - long tubes with special spiral chitinous thickenings inside. They are located in the back of the abdomen.

Circulatory system in spiders open . The heart looks like a long tube located on the dorsal side of the abdomen. Blood vessels extend from the heart. Like crustaceans, spiders have hemolymph circulating in their bodies.

Excretory system represented by two long tubes - Malpighian vessels . One end of the Malpighian vessels ends blindly in the body of the spider, the other opens into the hind intestine. Metabolic products are removed through the walls of the Malpighian vessels, which are then excreted. Water is absorbed in the intestines. In this way, spiders save water, so they can live in dry places.

Nervous system the spider consists of the cephalothoracic ganglion and numerous nerves extending from it.

Reproduction. Fertilization in spiders is internal. Mating of crosses occurs at the end of summer. The male transfers sperm to the female's genital opening using special outgrowths located on the front legs. Spiders have poor vision; they see poorly with the help of 8 simple eyes. The male needs to be very careful so that the female does not mistake him for prey. Immediately after mating, the spider hastily leaves, since the behavior of the female can change dramatically, and slow males are often killed and eaten.

By autumn, the female lays several hundred eggs in cocoon from the web. He hides it under the bark, under the stones. By winter it dies. In the spring, spiders crawl out of the cocoon, climb up the branches and, with gusts of wind, fly away on the web and settle. The complex behavior of a spider: the construction of trapping nets, flight devices, and dwellings is instincts , i.e. behavioral norms characteristic of each species that are inherited.

Arachnids are primarily terrestrial arthropods. They breathe using lungs or tracheas. Their body is divided into a cephalothorax and abdomen, or it is fused. Externally, arachnids can be distinguished from other arthropods by the following characteristics: they have no antennae, two pairs of mouthparts, and four pairs of walking legs. The complex behavior of spiders (building trapping nets, cocoons) is based on instincts.