Signs characteristic of the cross spider. arachnids

Cross spiders are a genus of the class of arachnids with about 2 thousand species. They are widespread and are typical representatives of their class.

Crosses live in forests, gardens, meadows. Weave a web between branches, on buildings, etc. They feed on small insects.

The size of representatives of cross-spiders is from 1.5 to 4 cm in females and about 1 cm in males.

The chitinous cuticle of cross spiders is quite thin. The body is subdivided into a small, slightly elongated, non-segmented cephalothorax and a large, in comparison with it, non-segmented, rounded abdomen. A lighter pattern in the form of a cross is formed on top of the abdomen. Hence the name of these spiders.

There are four pairs of walking legs on the cephalothorax. In front of them are chelicerae (jaws) and pedipalps (mandibles). With the help of the first, the cross-spider kills the victim. Their terminal segments are transformed into claws, in which ducts of poisonous glands open. The poison has a paralyzing effect. Pedipalps are used to hold the victim, turn it over, and they also have many organs of touch.

At the end of the abdomen there are six arachnoid warts (three pairs). They open the ducts of the spider glands, which can be about 1000. Cross spiders secrete various types of webs. Some are sticky, others are more durable. When released, the web hardens in air, turning into a fairly strong thread. Spiders weave trapping nets, shelters, cocoons from the web, bind the victim with it. The trapping web of the spider-cross consists of a strong polygonal base and radial supports and sticky concentric circles. From the central part of the network, a thread departs to the spider's shelter. The oscillations of the web when the victim hits it are transmitted along this thread to the spider, and it crawls out of the shelter.

The spider-cross injects into the victim not only poison, but also digestive juices, which break down its tissues, turning it into a liquid slurry. Extraintestinal digestion lasts about an hour. The spider can only eat liquid food, which is completely digested inside its digestive system. The suction of food occurs due to the muscular pharynx. There is a stomach, a branched midgut, into which the ducts of the liver open. This is where absorption takes place. nutrients into the hemolymph (arthropod blood mixed with lymph). Undigested residues go into the hindgut and are excreted through the anus.

The circulatory system is characteristic of all arthropods: open. On the dorsal side of the abdomen there is a tubular heart. From the heart, the hemolymph is pushed through the vessels to the front of the body, then it pours into the spaces between the organs and flows in the abdominal direction, where it is enriched with oxygen. After that, the hemolymph is again collected in the vessels and sent to the heart.

The respiratory system of the spider-cross consists of a pair of lung sacs and trachea. The lungs are located in the anterior part of the abdomen, contain many leaf-like folds, in which a lot of hemolymph flows. Tracheas are thin bundles of tubes that run through the body. They do not need hemolymph as an intermediary for the transfer of oxygen.

In cross-spiders, the excretory organs are represented by malpighian vessels, whose ducts open into the extension of the hindgut (cloaca), and coxal glands, the ducts of which open at the base of the first pair of walking legs.

In the ventral nerve chain in cross-spiders, the ventral ganglia merge. There are 8 simple eyes, which, like all arachnids, see poorly. The organs of touch, represented by sensitive hairs, are well developed. There are organs of smell and chemical sense.

Spider-spiders have pronounced sexual dimorphism. Females are larger and kill males after fertilization. The sex glands are paired, their common duct opens on the abdomen. The male delivers his sexual products to the female with the help of pedipalps. After fertilization, the female spins a cocoon using a soft silky web. Then it lays eggs in a cocoon, in which small spiders develop, i.e., the development of cross-spiders is direct.

About 25 thousand species of arachnids are known. These arthropods are adapted to living on land. They are characterized by respiratory organs. As a typical representative of the class Arachnids, consider the cross-spider.

The external structure and nutrition of arachnids

In spiders, the segments of the body merge, forming the cephalothorax and abdomen, separated by interception.

The body of arachnids is covered chitinized cuticle and the underlying tissue (hypoderm), which has a cellular structure. Its derivatives are spider and poisonous glands. The poisonous glands of the cross spider are located at the base of the upper jaws.

A distinctive feature of arachnids is the presence six pairs of limbs. Of these, the first two pairs - the upper jaws and leg tentacles - are adapted to capture and grind food. The remaining four pairs perform the functions of movement - these are walking legs.

During embryonic development, a large number of limbs are laid on the abdomen, but later they are transformed into spider warts, opening the ducts of the spider glands. Hardening in air, the secretions of these glands turn into cobwebs, from which the spider builds a trapping web.

After the insect has got into the net, the spider wraps it in cobwebs, sticks the claws of the upper jaws into it and injects poison. It then leaves its prey and hides for cover. The secret of poisonous glands not only kills insects, but acts as digestive juice. After about an hour, the spider returns to its prey and sucks out semi-liquid, partially digested food. From the killed insect, one chitinous cover remains.

Respiratory system in the cross-spider, it is represented by lung sacs and tracheae. lung bags and the tracheae of arachnids open outward through special openings on the lateral parts of the segments. In the lung sacs there are numerous leaf-like folds in which blood capillaries pass.

Trachea They are a system of branched tubules that go directly to all organs, where tissue gas exchange takes place.

Circulatory system arachnids consists of a heart located on the dorsal side of the abdomen and a vessel through which blood moves from the heart to the front of the body. Since the circulatory system is not closed, blood returns to the heart from the mixed body cavity (myxocoel), where it washes the lung sacs and trachea and is enriched with oxygen.

excretory system The spider-cross consists of several pairs of tubes (Malpighian vessels) located in the body cavity. Of these, waste products enter the posterior intestine.

Nervous system arachnids are characterized by the fusion of nerve nodes with each other. In spiders, the entire nerve chain merges into one cephalothoracic ganglion. The organ of touch is the hairs that cover the limbs. The organ of vision is 4 pairs of simple eyes.

Reproduction of arachnids

All arachnids are dioecious. The female cross-spider lays eggs in autumn in a cocoon woven from a silky web, which she attaches in secluded places (under stones, stumps, etc.). By winter, the female dies, and spiders emerge from the eggs that have overwintered in a warm cocoon in the spring.

Other spiders also take care of their offspring. For example, a female tarantula carries her young on her back. Some spiders, having laid their eggs in a web cocoon, often carry it with them.

• Araneus mitificus or "Spider Pringles“

a typical representative of the Asian fauna, distributed from India, Nepal and Bhutan to Australia. A notable feature of the cross-spider is an exact replica of the mustachioed face found on packages of Pringles chips, located in place of the traditional cross. These spiders hunt only from ambush, and their webs are always missing one section, but there is a signal thread stretched into the shelter. The size of adult females is 6-9 mm, males - 3-5 mm, but the modest size does not prevent the spiders from proudly wearing the “face” of popular chips.

• Araneus ceropegius, Aculepeira ceropegia)

lives in thickets of bushes and tall grass of forest edges, groves and gardens of the temperate climate zone. Oak crosses live in Europe, Russia, northern Africa, as well as in Asian countries north of the Himalayas, excluding the Arabian Peninsula. For females and males, the abdomen is pointed at both poles and the cephalothorax is well pubescent. The length of the female cross is 1.2-1.4 cm, the male is 0.7-0.8 cm. The upper side of the brown abdomen is decorated with a light “herringbone”, there is an elongated yellow spot below.

• or meadow cross(Araneus quadratus)

found in damp, open grassy areas. Lives in Europe, Central Asia, Russia, Japan. The shape, size and color is very similar to the common cross. On the upper part of the abdomen, the cross-spider has 4 round light spots or 4 dark dots, depending on the main color of the body. Below is a blurred leaf-like pattern. The base color of the body varies from light green and carmine to black-brown. There may be light stripes on the paws. The length of females is 1.7 cm, males are two times shorter. Adult female cross spiders can change color and blend in color with their surroundings.

• Araneus sturmi

a rare orb-web spider, lives mainly in coniferous forests in the Palearctic region (Europe, Russia, Asia north of the Himalayas, north Africa). The maximum body length of these spiders is 5.5 mm, females are usually longer than males: the length of females is 5-5.5 mm, the length of males is 4 mm. The modest dimensions of the cross are compensated by the variety of colors. The usual color of individuals of both sexes is reddish-brown, but very beautiful, red-yellow-green specimens are found. A distinctive feature of this species of cross-spider is “epaulettes”, dark areas in the front of the abdomen.

• (Araneus alsine)

a typical inhabitant of moist deciduous forests of the temperate zone. Outwardly, this spider resembles a meadow cross and has 4 similar large spots on the abdomen, but differs in color, which is dominated by orange and beige tones. The belly of the spider is dotted with small light spots, so the spider looks like (hence its English name "strawberry spider" - strawberry spider). The females of the chilly cross grow from 7 to 13 mm, the length of the males is 5-6 mm.

The cross-spider can be found in the forest, park, on the window frames of village houses and cottages. Most of the time, the spider sits in the center of its trapping web of sticky thread - cobwebs.

The body of the spider consists of two sections: a small elongated cephalothorax and a larger spherical abdomen. The abdomen is separated from the cephalothorax by a narrow constriction. Four pairs of walking legs are located on the sides of the cephalothorax. The body is covered with a light, strong and rather elastic chitinous cover.

The spider periodically molts, shedding its chitinous cover. During this time it grows. At the front end of the cephalothorax there are four pairs of eyes, and below a pair of hook-shaped hard jaws - chelicerae. With them, the spider grabs its prey.

There is a canal inside the chelicerae. Through the channel, the poison from the poisonous glands located at their base enters the body of the victim. Next to the chelicerae are short, covered with sensitive hairs, the organs of touch - the leg tentacles.

At the lower end of the abdomen there are three pairs of arachnoid warts that produce cobwebs - these are modified abdominal legs.

The liquid released from the spider webs instantly hardens in the air and turns into a strong cobweb thread. Different parts of spider warts secrete different types of webs. Spider threads vary in thickness, strength, stickiness. The spider uses various types of webs to build a trapping web: at its base, the threads are stronger and not sticky, and the concentric threads are thinner and stickier. The spider uses the web to strengthen the walls of its shelters and to make cocoons for its eggs.

Internal structure

Digestive system

The digestive system of a spider consists of a mouth, pharynx, esophagus, stomach, intestines (anterior, middle and posterior). In the midgut, long blind outgrowths increase its volume and absorption surface.

Undigested residues are brought out through the anus. The spider cannot eat solid food. Having caught prey (any insect), with the help of a web, he kills it with poison and lets digestive juices into his body. Under their influence, the contents of the caught insect liquefies, and the spider sucks it up. Only an empty chitinous shell remains from the victim. This type of digestion is called extraintestinal.

Circulatory system

The spider's circulatory system is not closed. The heart looks like a long tube located on the dorsal side of the abdomen.

Blood vessels branch off from the heart.

In a spider, the body cavity has a mixed nature - in the course of development it arises when the primary and secondary body cavities are connected. Hemolymph circulates in the body.

Respiratory system

The respiratory organs of the spider are the lungs and trachea. Lungs, or lung sacs, are located below, in front of the abdomen. These lungs evolved from the gills of the distant ancestors of aquatic spiders.

The spider-cross has two pairs of non-branching tracheas - long tubes that deliver oxygen to organs and tissues. They are located in the back of the abdomen.

Nervous system

The nervous system of a spider consists of the cephalothoracic ganglion and numerous nerves extending from it.

excretory system

The excretory system is represented by two long tubules - Malpighian vessels. With one end, the Malpighian vessels blindly end in the body of the spider, with the other they open into the posterior intestine. Out through the walls of the Malpighian vessels harmful products life, which are then brought out. Water is absorbed in the intestines. Thus, spiders conserve water, so they can live in dry places.

Reproduction. Development

Fertilization in spiders is internal. The female cross spider is larger than the male. The male carries the spermatozoa into the female genital opening with the help of special outgrowths located on the front legs.

She lays her eggs in a cocoon woven from a thin silky cobweb. The cocoon weaves in various secluded places: under the bark of stumps, under stones. By winter, the female cross spider dies, and the eggs hibernate in a warm cocoon. In the spring, young spiders come out of them. In autumn, they release cobwebs, and on them, like on parachutes, they are carried by the wind over long distances - spiders are resettled.

Arachnoids, or arachnids, are one of the most ancient living creatures on Earth. The characteristic features of the structure of arachnids are due to the existence on land and a predatory lifestyle.

External structure

The external structure of arachnids is different. In spiders, the body is divided into sections:

• elongated cephalothorax;
• wide belly.

Between the two parts of the body is a narrow constriction. The cephalothorax is equipped with organs of vision and digestion. Spiders have several simple eyes (from 2 to 12) that provide a circular view.

On the sides of the mouth grow hard curved jaws - chelicerae . With them, the predator grabs its prey. Chelicerae are equipped with venom ducts that are injected into the body at the time of the bite. The first pair of limbs serves to protect during an attack.

The oral apparatus of arachnids is complemented by a second pair - leg tentacles . With them, the spider holds the victim while eating. They also function as organs of touch. The mouth tentacles are covered with many villi. The hairs sensitively pick up the slightest vibrations of the surface and air, help the spider to navigate in space, to feel the approach of other creatures.

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To the question: how many antennae a spider has, it is not difficult to answer. Arachnids do not have antennae.

On the sides of the cephalothorax are 4 pairs of limbs. The comb claws on the hind legs are designed for weaving webs.

It is visually easy to see what cover the spiders have on their bodies. They are protected by a strong chitinous shell. In the process of growth, it periodically changes during molting.

Rice. 1 Spider - cross

Internal structure

The peculiarity of the structure of arachnids is noticeable in the organization of the body cavity. It is a combination of primary and secondary cavity. The body is filled with hemolymph. The heart is located in the dorsal part of the abdomen and looks like a long tube. Blood vessels branch off from it. Circulatory system is not closed.

Spider blood is colorless.

Respiratory system presented:

• tracheae ;
• lung sacs .

Breathing is adapted to life on land. Spiders breathe with the help of trachea, which resemble two long tubes with numerous holes. They carry oxygen to the internal organs.

Digestive system consists of:

• mouth ;
• pharynx ;
• stomach ;
• anterior, middle and hindgut ;
• cesspools .

excretory system arachnids are arranged in an unusual way. The excretory organs are two Malpighian vessels. These are tubes at one end that go into the internal cavity of the body, and at the other - into the intestines. Waste materials pass through the walls of blood vessels. The end products are brought out, and the liquid remains inside the body. Thus, spiders retain moisture and can live in arid conditions for a long time.

Let's study what nervous system in arachnids. It is called nodal because the main center forms 5 pairs of nerve nodes. A nerve chain runs along the abdomen.

IN sexual reproduction both males and females participate. Females are larger in size and often eat a partner. After fertilization, the female lays eggs and weaves a cocoon around them.

Rice. 2 Cocoon

The maximum number of eggs is 20 thousand.

After the appearance of the offspring, the mother looks after him for some time. The development of the young depends on the variety.

Web

Creation

Spiders have their own hunting equipment - a hunting net, in the form of a web. On the abdomen are arachnoid warts, equipped with special glands. A thin, but extremely strong thread is produced from them. The glands of arachnids produce a special substance that quickly hardens in the air. Spider thread has different characteristics and purpose:

• non-adhesive, but strong for the network frame;
• adhesive and thin for mesh cells;
• soft for a cocoon with eggs and burrow walls.

Rice. 3 Web

Meaning

Spiders set their traps among the thickets and hide in a secluded place. When an insect enters the net, the vibrations of the threads inform the hunter about the prey. He tightly wraps the victim with a sticky substance and then injects a poisonous secret into it. This fluid acts like digestive juice. She softens the prey. After that, the predator sucks in the resulting slurry. This method of nutrition is called extraintestinal.

The thread helps the spider move in space. With her help, he descends from a height, finds a way to his shelter.

A giant web has been discovered in Madagascar. It was woven by Darwin's spider. The diameter of a miracle is a network of 25 meters.

Spider thread in its appearance and properties resembles silk. Residents of tropical islands make small fishing nets from it. In the old days, cobwebs were applied to wounds instead of dressings.

What have we learned?

The body of arachnids consists of several connected parts. Distinctive features of the structure: oral limbs with poisonous ducts, extraintestinal digestion, the presence of arachnoid glands.

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