Spider spider description for children. Class Arachnids - spider-cross. Excretory system and digestion

Belongs to the orb-web family, the genus of araneomorphic spiders. In total, there are more than 1000 species of representatives of this genus in the world, but in Russia and the CIS countries, you can find from 15 to 30 species.

Habitat

The crosses live mainly in humid and damp places - in fields, meadows, forests, along the banks of reservoirs and rivers.

Spider cross

Spider cross

The structure of the spider spider

Dimensions, description
The size of the male is 10-11 mm, the female is larger - 17-26 mm. The cross has 8 legs and a large rounded abdomen. On the upper side of the spider's abdomen, white or light brown spots form a kind of cross, hence the name of the spider was born. The spider has 4 pairs of eyes, like most spiders; they look in different sides, providing its owner with a fairly broad outlook. Nevertheless, spiders see poorly, they are short-sighted and distinguish mainly shadows, movement, contours of everything that surrounds them.

Features of the spider spider

Spiders are dioecious animals. After mating, the male dies, and the female begins to weave a cocoon from the web for eggs, which usually lays in autumn. The cocoon is quite dense; for some time the female carries it on herself, and then hides it in any safe place - in a crack in the bark of trees or behind a lagged piece of bark. In spring, young (juvenile) spiders emerge from the cocoon. They become sexually mature by the end of summer, after which the female that gave birth to them dies.

In the first days of his life, the male cross spider also builds a network - he needs something to feed on. But upon reaching maturity, he begins to wander in search of adventure and, of course, noticeably loses weight. During this period, he is driven by only one desire - to find the female's web.

When the female's web is found, he makes every effort not to get to her for lunch. To do this, he weaves for himself a thread down from the edge of the web - for retreat. Then he gently twitches the thread. The female immediately rushes in search of prey, and the male retreats down the rescue line.

This is repeated several times - until the female realizes that it is not the prey that pulls the web, but her long-awaited partner. Then she changes her anger for mercy, and the spiders mate. But the male must not lose vigilance, because after mating, the hunting instinct awakens in the female again. If he does not escape in time, he may well be eaten.

Reproduction of the spider spider
In the cocoon, which the female weaves in autumn, there are from 300 to 800 amber eggs. Under the protection of the cocoon, future spiders are not afraid of either the cold or the flood - it is very light and does not get wet. In the cocoon, the eggs wait out the winter, and in the spring, small spiders emerge from the eggs. For a while they sit inside the cocoon, afraid to leave such a cozy refuge. But they gradually spread out and begin to live independently.

It is clear that it will be very difficult for such a huge offspring to get settled in life. The competition is very high, someone will die of hunger, and someone will be eaten by relatives. Therefore, young spiders face a serious task - to disperse as quickly as possible in order to increase their chances of survival.

Their legs are small, weak, so the spiders move, gliding with the help of their web, like real aeronauts. With a favorable wind, a spider can fly a distance of 300-400 km. When the wind dies down, the cobweb falls to the ground, the spider throws it and begins to settle in a new place. If he is lucky with the site, he will be able to catch up to 500 insects per day with his nets. The hunt goes on constantly.

According to the calculations of naturalists, millions of spiders live in meadows, fields and forests, destroying whole legions of insects, including those dangerous to humans and their economy. If it were not for the spiders, the number of flies, mosquitoes, mosquitoes, midges, moths and aphids would be several orders of magnitude higher and could seriously poison our lives. Experts do not even exclude the possibility of using spiders in biological pest control.

The spider either eats the caught prey immediately on the spot, or, if not too hungry, drags it into a secluded corner or entangles it with cobwebs. Around the cobwebs under the leaves, you can find a whole grocery store of cobwebbed flies harvested for a rainy day.

Spider spider behavior

How does a spider hunt? When a fly or any other insect enters the web, the spider feels the vibration of the trapping net, it picks up in the victim and kills it with a bite of poisonous jaws, or chelicera. The fly stops shaking the web, and the spider calmly swaddles it with a bundle of thin threads, pulling them out of the abdomen with a pair of its legs.

After biting the surrounding threads, the spider takes its breakfast and goes to the center of the web - to have a meal. He crumples his prey, injecting digestive juices into it. When the fly has digested inside its shell, the spider sucks in the semi-liquid contents, which the fly has turned into, and throws out the victim's skin. During a successful hunt, the spider can eat about a dozen flies in one sitting. The poison of the crosses is dangerous only for small insects, it cannot harm a person.

Habitat

The crosses live mainly in the crowns of trees, they make a secluded shelter from the leaves, and the cobwebs are pulled between the branches. Webs can be found in a forest, grove, or neglected garden. Sometimes it can be found in bushes or in window frames and under the eaves of abandoned houses.

The fishing net constantly requires repair, it is destroyed by both small and large insects, so every couple of days the spider-spiders spread the web and make a new one. They usually do this at night, and by morning the new web is ready for new prey. Thus, the spider is relatively safer at night, because its natural enemies, insectivorous birds, sleep at night. He does not need light to build a web; a well-developed sense of touch is quite enough.

The enemies of the cross spider are also flies and wasps, which lay eggs in the bodies of their victims. For example, the melanophore swarm fly - taking advantage of the immobility of a spider, it can fly up to it, sit on its back and, in the blink of an eye, lay an egg in its body.

Spider's web
The female spider's web has exactly 39 radii, 1245 points of attachment of the radii to the spiral and 35 turns of the spiral - no more, no less. The web of all spiders is like one another like two drops of water, because all the necessary data is genetically fixed in their heredity. Therefore, even small spiders know how to build cobwebs and catch prey.

Any cobweb is not only beautiful in its symmetry and delicacy, it is very rationally arranged. All the threads that form it are very light and, nevertheless, very strong, and are connected in such a way that they only work to break.

How does a spider manage to build such an even symmetrical web, which exceeds its size by several tens of times? A spider (more precisely, a spider), having climbed onto a branch or trunk of a tree, releases a long cobweb thread from its abdomen. A stream of air picks it up, and the spider waits patiently until the thread snags on something suitable.

If this does not happen, and the thread hangs, the spider pulls it to itself and eats it. Then he runs to another place and tries again. And so on until the thread caught. Then the spider crawls to the hooked end of the thread and fixes it well. Then it descends on its own thread to some support. There he also firmly fixes this thread - now 2 threads are already fixed.

Along the second thread, the spider returns and drags the third, it fixes it at the starting point, i.e. where the first thread came from. The triangular frame - the basis of the future web - is ready. Inside this frame, the spider stretches several strands that intersect in the center. The spider marks the center of the web in a lump and begins to stretch out all its numerous radii from it, fastening them with a spiral thread, and then lays trapping threads. At the intersection points of the spiral and the radius, the spider connects them with its legs.

Note that the angles between all the radii and the distance between the turns of the web are strictly constant values. How does such a small creature manage to keep its web in strict accordance with geometry? For this, you need at least the simplest measuring device. And, imagine, the spider has it! This is his first pair of legs that can act as a scale bar.

While working on the web, the spider regularly checks the distance between the spirals. Its natural instrument is so precise and reliable that it allows you to work in pitch darkness. The final chord in the creation of the web will be the signaling network, the end of which is laid down to the spider's shelter. It takes a spider several hours of painstaking work and about 20 meters of web to build the entire web.

Chemically, spider webs are a complex protein polymer called fibroin. The many glands of the spider's abdomen form this viscous liquid, which quickly solidifies in air in the form of the finest filaments. The spider can produce several different types cobwebs with different properties. For the frame of the web, he makes a dry and thick thread, for the cocoon - silky and soft, for the trapping spiral - thin and sticky. Why doesn't the spider itself stick to its web? Everything is very simple - it runs only along non-sticky threads, and carefully avoids touching the sticky spirals.

The polymer fluid enters the outside from the glands on the abdomen of the spider through thin tubes and solidifies in very thin filaments. If a spider needs special strength, it can weave several of these threads together. Scientists in last years are seriously studying the properties of spider "silk". It turned out that it has many unique properties.

The manufacturing technology of spider webs is akin to the production of synthetic fibers. But in terms of strength, no synthetic fiber can be compared with a spider one - it can withstand a load of up to 260 kg per 1 sq. Mm, which is superior in strength to steel. That is why the inhabitants of the tropics make nets from the cobweb for catching birds, bats, insects, and even weave fishing tackle.

The web is so elastic that it can stretch up to 30% of its length and contract back to its original length. Its lightness and subtlety unwittingly amaze, because 340 grams of cobweb is enough to encircle the globe along the equator!

The use of a spider web in the household and medicine
People have long tried to make fabric based on spider webs. In Germany, back in the 16th century, ribbons and various decorations were woven from spider webs in villages. Then, in France, artisans came up with the idea of ​​making gloves and stockings from cobwebs, which caused the utter delight of fashionistas.

But it turned out to be impossible to launch this technology into large-scale production, and this was convincingly proved by the physicist and zoologist Reaumur. For such production to become profitable, it is necessary to maintain and feed hundreds of thousands of spiders. But to feed them, you would have to catch several million flies every day, which was absolutely impossible to implement in practice.

However, people still use the web, even today. For sighting devices (crosshairs) in various optical devices (microscopes, telescopes, sights, etc.), the spider's web is just perfect. Microbiologists have also found a use for it, having developed a unique air analyzer with its help.

The spider-cross is launched on a special frame, fed, and the spider weaves its web on the basis of this frame. Then, air is pumped through the frame with a network, and the thinnest cobweb perfectly captures the microbes that are in the air. This method of analyzing air has been recognized as the most effective of all existing in the world.

In folk medicine, spider webs have been used since ancient times to disinfect open wounds. Studies have confirmed that spider webs kill bacteria, and have been used to develop drugs that are harmless to animals but deadly to all kinds of bacteria. As you can see, the spider-cross is extremely useful for humans, in every sense.

there are at least 12 detachments, the most important of which are the Spiders, Scorpions, False Scorpions, Solpugs, Haymakers, Ticks.

Arachnids differ in that they do not have antennae (antennae), and the mouth is surrounded by two pairs of peculiar limbs - chelicerae and jaw, which the Arachnids call pedipalps... The body is divided into the cephalothorax and abdomen, but in ticks all sections are fused. Walking legs four pairs.

Spider spiders these are common members of the Arachnid class. Spider spiders This is the collective name of several biological species of the genus Araneus of the family Orb-weaving spiders of the order Spiders. Cross spiders are found in the warm season throughout the European part of Russia, in the Urals, in Western Siberia.

Cross spiders are predators that feed only on living insects. The spider-spider catches its prey with a very complex, vertical wheel-shaped trapping net(hence the name of the family - Orb-web spiders) . The spider spinning apparatus, which ensures the manufacture of such a complex structure, consists of external formations - spider warts- and from internal organs - spider glands. A droplet of sticky liquid is released from the spider warts, which, when the spider moves, is pulled into the finest thread. These threads quickly thicken in the air, turning into a strong cobweb thread... The web is made up mostly of protein. fibroin... In terms of chemical composition, the spider's web is close to the silk of silkworm caterpillars, but more durable and elastic. The breaking load for spider webs is 40-261 kg per 1 sq mm of thread cross section, and for silk it is only 33-43 kg per sq mm of thread cross section.

To weave its trapping net, the Cross Spider first stretches especially strong threads in several convenient places, forming a support frame for the future network in the form of an irregular polygon. Then he moves along the upper horizontal thread to its middle and, going down from there, draws a strong vertical thread. Further, from the middle of this thread, as from the center, the spider conducts radial threads in all directions, like the spokes of a wheel. This is the backbone of the entire web. Then the spider starts to weave from the center spiral threads attaching them to each radial thread with a drop of adhesive. In the middle of the net, where the spider itself then sits, the spiral threads are dry. Other spiral threads are sticky. Insects that fly onto the net stick to them with their wings and paws. The spider itself either hangs head down in the center of the spider web, or hides in

Class Arachnids Cross-spider

to the side under the sheet - there he has asylum... In this case, he stretches towards himself from the center of the web a strong signal a thread.

When a fly or other insect enters the net, the spider, feeling the trembling of the signal thread, rushes out of its ambush. Plunging the claws of a chelicera with poison into the victim, the spider kills the victim and secretes digestive juices into its body. After that, he entangles a fly or other insect with a cobweb and leaves it for a while.

Influenced by secreted digestive juices internal organs the victims are quickly digested. After some time, the spider returns to the victim and sucks everything out of it. nutrients... From the insect in the web, only an empty chitinous cover remains.

Making a trapping net is a series of interconnected unconscious actions. The ability to do this is instinctive and inherited. It is easy to be convinced of this by following the behavior of young spiders: when they come out of their eggs, no one teaches them how to weave a trapping net, the spiders immediately very skillfully weave their webs.

In addition to the wheel-shaped trapping nets, other types of spiders have nets in the form of a random interweaving of threads, nets in the form of a hammock or canopy, funnel-shaped nets and other types of trapping nets. The spider's web is a kind of adaptation outside the body.

I must say that not all types of spiders weave trapping webs. Some are actively looking for and catching prey, while others lie in wait for it from an ambush. But all spiders have the ability to secrete webs, and all spiders are made from webs. egg cocoon and spermatic nets.

External structure... The body of the Cross Spider is subdivided into cephalothorax and abdomen which connects to the cephalothorax with a thin movable stalk... There are 6 pairs of limbs on the cephalothorax.

The first pair of limbs - chelicerae that surround the mouth and serve to capture and puncture prey. Chelicerae consist of two segments, the end segment looks like curved claws. At the base of the chelicera are poison glands, the ducts of which open at the tips of the claws. Spiders with chelicera pierce the integuments of the victims and inject poison into the wound. Spider venom has a nerve effect. In some species, for example, in Karakurt, in the so-called tropical Black widow, the poison is so strong that it can kill

Class Arachnids Cross-spider

even a large mammal (instantly!).

The second pair of cephalothoracic limbs - pedipalps have the appearance of articulated limbs (they look like short legs sticking out forward). The function of the pedipalps is to feel and hold the prey. In sexually mature males, on the terminal segment of the pedipalp, copulatory apparatus, which the male fills with sperm before mating. During copulation, the male uses the copulatory apparatus to inject sperm into the female's sperm. The structure of the copulatory apparatus is species-specific (i.e., each species has a different structure).

All arachnids have 4 pairs walking legs... The walking leg consists of seven segments: basin, swivel, hips, cups, shins, precuts and paws armed with claws.

Arachnids have no antennae. On the front of the cephalothorax, the spider-spider has two rows of eight simple eyes... Other types of eyes may have three pairs, or even one pair.

Abdomen in spiders it is not segmented and has no true limbs. There is a pair of pulmonary sacs, two beams trachea and three pairs cobweb warts... Spider-spider spider warts consist of a huge number (about 1000) cobweb glands that produce various types of cobwebs - dry, wet, sticky (at least seven varieties of very different purposes). Different types cobwebs perform various functions: one is for catching prey, the other is for building a dwelling, the third is used in the manufacture of a cocoon. Young spiders also settle on special webs.

On the abdominal side of the abdomen, closer to the junction of the abdomen with the cephalothorax is located sexual hole... In females, it is surrounded and partially covered by a chitinized plate. epigine... The structure of the epigina is species-specific.

Body covers. The body is covered with chitinized cuticle. The cuticle protects the body from external influences. The most superficial layer is called epicuticle and it is formed by fat-like substances, therefore, the integuments of spiders are impermeable to either water or gases. This allowed spiders to colonize the driest regions of the globe. The cuticle simultaneously performs the function

Class Arachnids Cross-spider

outdoor skeleton: serves as a site for muscle attachment. From time to time, spiders shed, i.e. shedding the cuticle.

Musculature arachnids consists of striated fibers that form powerful muscle bundles, i.e. the musculature is represented by separate bundles, and not by a bag like in worms.

Body cavity. The body cavity in Arachnids is mixed - mixocel.

Digestive system typical, consists of front, average and back intestines. The anterior gut is presented mouth, by the throat, short esophagus and stomach... The mouth is surrounded by chelicerae and pedipalps, with which spiders grab and hold prey. The pharynx is equipped with strong muscles for absorbing food gruel. Ducts open into the anterior intestine salivary glands, the secret of which effectively breaks down proteins. All spiders have the so-called extraintestinal digestion... This means that after killing the prey, digestive juices are introduced into the victim's body and the food is digested outside the intestines, turning into a semi-liquid gruel, which is absorbed by the spider. In the stomach, and then in the midgut, food is absorbed. The midgut has long blind lateral protrusions, increasing the area of ​​absorption and serving as a place for temporary storage of food mass. The ducts also open here liver... She highlights digestive enzymes and also ensures the absorption of nutrients. Intracellular digestion takes place in the liver cells. On the border of the middle and rear sections, the excretory organs flow into the intestine - malpighian vessels... The hindgut ends anal hole located at the posterior end of the abdomen above the arachnoid warts.

Respiratory system... In some arachnids, the respiratory organs are represented pulmonary bags, other's tracheal system, for others - both at the same time. In some small arachnids, including some of the ticks, the respiratory organs are absent, breathing is carried out through thin integuments. The lung sacs are more ancient (from an evolutionary point of view) formations than the tracheal system. It is believed that the gill limbs of the aquatic ancestors of arachnids sank into the body and formed cavities with pulmonary leaflets. The tracheal system arose independently and later than the pulmonary sacs, as organs more adapted to air breathing. Tracheas are deep incisions of the cuticle into the body. The tracheal system is perfectly developed in Insects.

Class Arachnids Cross-spider

In the Cross Spider, the respiratory organs are represented by a pair pulmonary sacs forming leaf-shaped folds on the ventral side of the abdomen, and two bundles trachea that open spiracles also on the underside of the abdomen.

Circulatory system open, comprises hearts, located on the dorsal side of the abdomen, and several large blood vessels extending from it vessels. The heart has 3 pairs of spines (holes). From the front end of the heart departs front aorta decaying into arteries. The terminal branches of the arteries pour out hemolymph(this is the name of the blood in all arthropods) into the system cavities located between the internal organs. Hemolymph washes all internal organs, delivering nutrients and oxygen to them. Further, the hemolymph washes the pulmonary sacs - gas exchange occurs, and from there it enters pericardium, and then through ostia- in heart. Arachnid hemolymph contains a blue respiratory pigment - hemocyanin, containing copper. Pouring out into the secondary body cavity, the hemolymph mixes with the secondary cavity fluid, therefore it is said that arthropods have a mixed body cavity - mixocel.

Excretory system arachnids have malpighian vessels that open into the intestine between the mid and hind intestines. Malpighian vessels, or tubules, are blind protrusions of the intestine that ensure the absorption of metabolic products from the body cavity. In addition to malpighian vessels, some arachnids also have coxal glands- paired saccular formations lying in the cephalothorax. From the coxal glands, convoluted canals depart, ending in urinary bubbles and output ducts, which open at the base of the walking limbs (the first segment of the walking legs is called coke, hence the name - coxal glands). The spider-spider has both coxal glands and malpighian vessels.

Nervous system... Like all Arthropods, Arachnids have a nervous system - ladder type... But in the Arachnids there was a further concentration of the nervous system. A pair of supraopharyngeal nerve ganglia is called the "brain" of the Arachnids. It innervates (controls) the eyes, chelicerae and pedipalps. All the cephalothoracic ganglia of the nerve chain merged into one large nerve node located under the esophagus. All abdominal nerve ganglia of the nerve chain also fused into one large abdominal nerve node.

Of all the senses, the most important thing for spiders is touch. Numerous tactile hairs - trichobothria- scattered in large numbers over the surface of the body, especially on the pedipalps and walking legs.

Class Arachnids Cross-spider

Each hair is movably attached to the bottom of a special fossa in the integument and is connected to a group of sensitive cells that are located at its base. A hair perceives the slightest vibrations of air or cobwebs, responsive to what is happening, while the spider is able to distinguish the nature of the irritating factor by the intensity of the vibrations. Tactile hairs are specialized: some register chemical stimuli, others - mechanical, others - air pressure, and the fourth - perceive sound signals.

The organs of vision are represented with simple eyes found in most arachnids. Spiders most often have 8 eyes. Spiders are short-sighted, their eyes perceive only light and shadow, the outlines of objects, but details and color are not available to them. There are organs of balance - statocysts.

Reproduction and development... Arachnids dioecious... Fertilization internal... Most arachnids lay eggs, but some arachnids have live births. Development without metamorphosis.

The spider-spider has a well-defined sexual dimorphism: the female has a large abdomen, while mature males develop on pedipalps copulative organs... In each spider species, the copulatory organs of the male approach the female's epigyne like a key to the lock, and the structure of the male's copulatory organs and the female's epigyne is species-specific.

Mating in Cross Spiders occurs at the end of summer. Sexually mature males do not weave trapping nets. They wander in search of female nets. Having found a catching net of a sexually mature female, the male, somewhere off to the side on the ground, or on some twig, or on a leaf, weaves a small spermatozoa in the form of a hammock. On this mesh, the male from his genital opening, which is located on the abdominal side of the abdomen closer to the junction of the abdomen with the cephalothorax, squeezes out a drop sperm... Then he sucks this droplet into the pedipalps (like a syringe) and proceeds to seduce the female. The spider's eyesight is weak, so the male needs to be very careful so that the female does not mistake him for prey. For this, the male, having caught some insect, wraps it in a web and presents this peculiar gift to the female. Hiding behind this gift as a shield, the male approaches his lady very slowly and extremely cautiously. Like all women, the spider is very curious. While she is looking at the presented gift, the male quickly climbs onto the female, applies his pedipalps with sperm to the female's genital opening and

• Class Arachnids Cross-spider

  performs copulation. The female at this moment is good-natured and relaxed. But, immediately after mating, the male must hastily leave, since the behavior of the spider after copulation changes dramatically: she becomes aggressive and very active. Therefore, sluggish males are often killed by a female and eaten. (Well, after mating, the male will die anyway. From an evolutionary point of view, the male is no longer needed: he has fulfilled his biological function.) This happens in almost all species of spiders. Therefore, in research, females are most often found, while males are rare.

  After copulation, the female continues to actively feed. In the fall, the female from a special web makes cocoon, in which he lays several hundred eggs. She hides the cocoon in some secluded place, for example, under the bark of a tree, under a stone, in the crevices of a fence, etc., and the female herself dies. Eggs overwinter at Cross Spiders. In the spring, young spiders emerge from the eggs, which begin an independent life. Molting several times, the spiders grow and by the end of summer reach sexual maturity and begin to reproduce.

Meaning. The role of spiders in nature is great. They act as consumers of the second order in the structure of the ecosystem (i.e., consumers of organic matter). They destroy many harmful insects. They are food for carnivorous birds, toads, shrews, snakes.

Questions for self-control

What is the classification of the type Arthropods?

What is the systematic position of the Cross Spider?

Where do Cross Spiders live?

What is the shape of the body of the Cross Spiders?

What is the spider's body covered with?

What body cavity is typical for a spider?

What is the structure of the spider's digestive system?

What are the features of digestion in spiders?

What is the structure of the spider's circulatory system?

How does a spider breathe?

What is the structure of the spider's excretory system?

What is the structure of the spider's nervous system?

What is the structure of the spider's reproductive system?

How does the Cross Spider reproduce?

What do spiders matter?

Class Arachnids Cross-spider

Rice. Cross spider: 1 - female, 2 - male and wheel-shaped hunting net.

Rice. The cross spider weaves a trapping net

Class Arachnids Cross-spider

Rice. Internal structure of the Cross-Spider.

1 - poisonous glands; 2 - pharynx; 3 - blind outgrowths of the intestine; 4 - Malpighian vessels; 5 - heart; 6 - pulmonary sac; 7 - ovary; 8 - oviduct; 9 - spider glands; 10 - pericardium; 11 - ostia in the heart.

In the garden, forest and other places you can always see a trapping net spider-spider(fig.75A). He himself either sits in the center of his web, or hides in a shelter nearby on a branch or trunk. If we throw a fly or some other small insect on his structure, he will immediately run to the prey beating in sticky nets.

The spider-cross is the most typical representative of the Spiders order, therefore, it is characterized by most of the vital processes of all spiders.

External structure

The body of the spider-spider consists of two sections: a small, elongated cephalothorax and a large spherical abdomen, between them there is a narrow interception. On the cephalothorax in front of the top there are 4 pairs of eyes, below - a pair of powerful jaws - chelicerae.

The top of each jaw has a movable sharp hook - with them the spider-cross grabs and kills the prey. At the base of the chelicera are poisonous glands, from them a canal extends in the jaw, opening at the end of the jaw hooks. Foot-toes are located near the jaws. They are thick, soft, covered with sensitive hairs - these are the organs of touch of the spider-spider. On the sides of the cephalothorax there are 4 pairs of long walking legs.

The abdomen is spherical, smooth above. The spider-cross has a light cruciform pattern in front of it - hence its name. There are no legs on the abdomen, but 3 pairs of arachnoid warts are located below at the end of the abdomen - from them the cobweb is released.

The cover of the cross spider is chitinous, light. The body cavity is mixed (like a crayfish).

Catching net (cobweb)

The cross spider builds a trapping net from sticky and non-sticky cobwebs (Fig. 75B). The females build the fishing net.

At the same time, at first, from non-sticky strong threads, he makes a base in the form of an irregular polygon. Then, in this frame, also from non-sticky threads, he pulls the radii. Finally, the spider winds an adhesive thread with a spiral around these radii. The prey that has fallen into the net (that is, adhered to the sticky threads) fights, trying to free itself. Feeling the shake of the web, the spider runs to the victim using non-sticky radial threads. If there is a fly in the net, the spider immediately kills it. If the prey is larger, for example, a butterfly, the spider preliminarily envelops it with a cobweb released immediately so that it turns into a matted cocoon. Material from the site

Rice. 75B. Spider's Catching Net

Nutrition

After killing prey, the spider does not immediately begin to eat it. It can only absorb liquid food. To do this, the spider lets a drop of saliva into the victim, which liquefies dense tissues. The saliva turns the contents of the fly into liquid food and the spider sucks it out. If the prey is large, then the spider repeats the same technique several times, and, in the end, only an empty chitinous shell remains of the prey. This is how all spiders feed.

Position in taxonomy (classification)

The spider-cross is one of the species of the numerous order of Spiders.

In the class of Arachnids, the cross spider is a typical representative of these animals. You can find out more about the features of this species in our material.

Description and habitat features

There are more than 2 thousand species of cross spiders in the world. On the territory of Russia and neighboring countries, there are up to 30 species.

A distinctive feature of this species are light spots on the upper side of the body, which form the so-called cross. Hence the name of the species - a cross.

Rice. 1. External signs spider-spider

The females of such spiders are much larger than the male. Its dimensions range from 17 to 40 mm, while the male is up to 11 mm long.

The body of the animal consists of two sections: the cephalothorax and abdomen. The cephalothorax has 6 pairs of limbs, 4 of which are walking legs. On the abdomen, the limbs are modified into arachnoid warts.

Like most spiders, the spider is a predator. He catches his prey on a web, which he weaves quite skillfully. At the time of the hunt, it can sit directly on the web, waiting for the victim.

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The digestion process takes place in part outside the body of the animal. Together with digestive juices, it injects its poison into the prey and waits until the "dish" is ready. All that remains is to drink the nutritious liquid contents of the insect that has fallen into the trap. Small insects are a favorite delicacy.

Rice. 2. An insect caught in a spider's web becomes food for a spider

Weaving spider webs

The spider-spider settles in the crowns deciduous trees... The branches are used for the basis of their nets, and the leaves make an excellent shelter in which to hide. Cobweb usually large sizes is located both in the crown of a tree and on shrubs.

After a day or two, the spider itself breaks its network, which becomes unusable and builds a new one. The fact is that the prey itself partially spoils the web, breaking the threads. Also, dry leaves get into it, which interfere with hunting.

The spider weaves a new web, mainly at night. At this time of day, insects do not interfere, and there are no enemies that can eat the hunter himself. In building, they are helped by the sense of touch, not sight.

In an adult female, the number of radii, spirals in the web has a certain amount. The distance between the turns is also important. From observations it has been established that the spider web has:

• 39 radii;
• spiral turns - 35;
• spiral attachment points and radii - 1245.

This accuracy is due to a genetically based instinct. Even juveniles can weave a web with the precision of an adult.

Rice. 3. Catching net

Is the cross spider dangerous?

The poison of the cross is toxic to both invertebrates and vertebrates. The cross is able to bite through the skin of a person, however, the amount of poison injected into the body will be insignificant. Therefore, a mild, rapidly passing pain may appear from the bite.

What have we learned?

The spider-cross in its structure is no different from other spiders. He hunts for a web, which he builds quickly and efficiently, renewing it in a day or two. The venom of this spider does not pose a particular danger to humans.

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Habitat and external structure of the cross spider

In the garden or in the forest in summer, walking along a narrow path, we often come across cobwebs. This is most often a trapping web of a cross-spider. Often the eight-legged builder himself sits at the center of his wheel-like network. Its body with a sharp transverse constriction in the middle - a stalk, or waist, separating a small front part, called cephalothorax, from the back - smooth spherical abdomen... The abdomen above on a dark background has a cruciform pattern (hence the name of the spider - cross). On the upper side of the cephalothorax, the organs of vision are located in front - 8 simple eyes. 8 walking legs extend from the cephalothorax below, and mouth organs are visible in front of them, namely: the first pair - jaw, the second pair is leg-tentacles... The legs have sensitive hairs that are part of the organs of touch.

Drawing: External structure spider-cross. Catching web of a spider-cross.

The spider is a predator, it is armed with devices for killing prey, which are most often different flies. Each jaw has a segment at its apex in the form of a sharp movable claw. Poisonous glands that produce poison are placed under the bases of the jaws. When the jaws pierce the victim's body, poison is injected through the holes of the jaw claws and kills him.

All abdominal segments are fused together. Three pairs are visible at its rear end spider warts which open spider glands... The semi-liquid substance released by them hardens in air, forming spider webs. The spider connects them with the comb claws of the hind legs into one common thread.

Cross-spider trapping net

The female cross spider builds a large trapping net from the spider's threads, stretching it vertically between the branches of bushes, near fences and in other places. First, a polygonal frame with rays converging in the center is constructed from thick, non-sticky threads. To this base, the spider weaves a long thin and very sticky thread, placing it in the form of a spiral.

Cross-spider hunting

While waiting for prey, the spider usually stays near the net in a hidden nest made of cobwebs. A signal thread is stretched from the center of the network to it. When a fly, small butterfly or other flying insect enters the net and begins to beat in it, the signal thread vibrates. At this sign, the spider rushes from its shelter to prey and densely enmeshes it with cobwebs. He sticks the claws of his upper jaws into it and injects poison into the victim's body. Then the spider leaves its prey for a while and takes refuge in a shelter.

Spider-spider feeding

The contents of the poisonous glands not only kill the prey, but also act as a digestive juice on it. After about an hour, the spider returns and sucks in the already partially digested liquid content of its prey, of which only the chitinous cover remains. The spider cannot eat solid food. Thus, in spiders, the preliminary digestion of food occurs outside the body.

Drawing: internal structure spider-spider

Breath of the spider-spider

In front of the abdomen lies a pair of pulmonary sacs, communicating with environment... The walls of the sacs form numerous leaf-like folds, inside which blood circulates. It is enriched with oxygen in the air between the folds. In addition to the pulmonary sacs, the spider has two bundles of respiratory tubes in its abdomen - trachea opening outward with a common breathing hole.

The circulatory system of the spider-cross

The circulatory system of the spider-spider is the same as that of cancer.

Reproduction of a spider-cross

The female cross spider is larger than the male. In autumn, she lays her eggs in a cocoon woven from a thin silky web. She weaves a cocoon in various secluded places - under the bark of stumps, under stones. By winter, the female spider dies, and the eggs hibernate in a warm cocoon. In the spring, young spiders come out of them.