What is the basis of the complex behavior of spiders to build. Project-research "biological forms of behavior of the orb-web spider". Hermit spiders are the most dangerous

Habitat, structure and lifestyle.

Arachnids include spiders, ticks, scorpions and other arthropods, more than 35 thousand species in total. Arachnids have adapted to life in terrestrial habitats. Only some of them, for example, the silver spider, passed into the water for the second time.

The body of arachnids consists of a cephalothorax and usually a non-segmented abdomen or fused. There are 6 pairs of limbs on the cephalothorax, of which 4 pairs are used for locomotion. Arachnids do not have antennae or compound eyes. They breathe with the help of lung bags, trachea, skin. The largest number of arachnid species are spiders and mites.

Spiders

settled in a variety of habitats. In sheds, on fences, branches of trees and shrubs, openwork wheel-shaped networks of a spider-cross are common, and in their center or not far from them are the spiders themselves. These are females. On the dorsal side of their abdomen, a pattern resembling a cross is noticeable. Males are smaller than females and do not make trapping nets. In residential premises, sheds and other buildings, a house spider is common. He builds a trapping net in the form of a hammock. The silver spider makes a cobweb nest in the water in the form of a bell, and around it it pulls trapping cobweb threads.

At the end of the abdomen are arachnoid warts with ducts of the arachnoid glands. The substance released in the air turns into spider webs. When building a trapping web, the spider, using the comb-like claws of its hind legs, connects them into threads of different thicknesses.

Spiders are predators. They feed on insects and other small arthropods. The spider grabs the caught victim with its tentacles and sharp upper jaws, injects a poisonous liquid into the wounds, acting as digestive juice. After a while, he sucks out the contents of the prey with the help of a sucking stomach.

The complex behavior of spiders associated with the construction of trapping webs, feeding or reproduction is based on a multitude of successive reflexes. Hunger causes a reflex of searching for a place to build a trapping net, the found place serves as a signal for highlighting the web, fixing it, etc. Behavior that includes a chain of successive innate reflexes is called instinct.

Ticks

scorpions

Predators. They have a long segmented abdomen, on the last segment of which there is a stinger with ducts of poisonous glands. Scorpions catch and hold their prey with tentacles, on which claws are developed. These arachnids live in hot regions (in Central Asia, in the Caucasus, in the Crimea).

The meaning of arachnids.

Spiders and many other arachnids exterminate flies and mosquitoes, which are of great benefit to humans. Many birds, lizards and other animals feed on them. There are many spiders that harm humans. The bites of a karakurt living in Central Asia, the Caucasus, and the Crimea cause the death of horses and camels. For a person, scorpion venom is dangerous, causing redness and swelling of the bitten place, nausea and convulsions.

Soil mites, processing plant residues, improve the structure of the soil. But grain, flour and cheese mites destroy and spoil food supplies. Herbivorous mites infect cultivated plants. Scabies mites in the upper layer of human skin (usually between the fingers) and animals gnaw through passages, causing severe itching.

The taiga tick infects humans with the causative agent of encephalitis. Penetrating into the brain, the pathogen affects it. Taiga ticks get encephalitis pathogens by feeding on the blood of wild animals. The causes of the disease with taiga encephalitis were clarified in the late 30s by a group of scientists headed by academician E.N. Pavlovsky. All people working in the taiga are given anti-encephalitis vaccinations.

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

And 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?

Special life of spiders

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

Arachnids also include mites 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" itself is invisible to us. But his web is quite noticeable!

The behavior of the spider-cross is due to its lifestyle and habitat. Forests, parks, gardens and various green spaces can all be home to members of this species. In human dwellings, it is also quite common to find araneus diadematus.

spider spider

The bodies of all spiders are similar:

• small cephalothorax;
• large belly ovoid;
• 8 legs.

According to the pattern on the surface of the back, similar to a cross, this species got its name. The so-called eyes (8 pairs) are located in front of the spider's cephalothorax. The mouth of the cross consists of several "details": a pair of jaw-claws with poisonous glands at the bases, as well as tentacles (chelicerae) - organs of touch.

The structural features of the spider-cross allow it to survive, attack and feed with the help of its powerful jaws. On the legs are comb-like 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 assistant for survival is touch with sensitive legs.

The method of feeding the cross

A builder and hunter, the cross-spider feeds on anything that falls into its traps. It can 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 the prey with its toenails, its jaw-hooks, the spider bites through it, injecting a paralyzing poison into the wound of the victim. At the same time, digestive juice enters its body, softening the insides of the fly.

With its insatiable appetite, this insect hunter is able to suck out more than a dozen flies at a time. If there are too many victims, the behavioral features of the cross-spider tell him to wrap the captives in a cocoon and leave "for later." Stocks are suspended from a trap on threads. Spiders are not adapted to eating solid food. But they can suck out the softened insides of insects. For this extra-intestinal mode of feeding, arachnids do not need stomachs.

How Spiders Reproduce

Only by the end of the summer period, eight-legged forest dwellers reach puberty. By observing what features of the structure and behavior of the cross-spider contribute to the reproduction of this species, biologists have found that females are more than twice as large as males. Living alone, only in the autumn the spider sets off to look for a “lady”. By attaching his thread to the female's trap and pulling it, he draws the attention of the female in this way. The mating that took place becomes the last event in the life of this male - the “lady” eats him after the fertilization process. Satiation instinct, nothing personal!

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

What makes a spider spin a web

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

• 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 arachnoid composition begins to stand out.
• Each action causes subsequent signals about the necessary continuation. Everything is arranged simply and clearly.

A spider's web-weaving skills can be innate, built-in, or acquired, depending on the environment. However, the overall layout of the web always has many of the same details. Perfectly woven spiral coils 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 web mesh.

About spiders, cobwebs and humans

Remembering the signs and scientific research, you can find out what features of the behavior and structure of the cross-spider were used by mankind to treat various diseases.

• By applying the removed fresh cobweb to a small wound, you can stop the bleeding.
• It is believed that the decoration with the image of a forest octopus brings monetary luck.
• European doctors 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" sits in the very center of his trap and does not crawl out, then it will definitely rain.
• If spiders weave fresh webs, then this is for 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 an almost leading role in the fight against insect pests. During the season, these gluttons destroy more than 200 kg of possible carriers of various infectious diseases on a hectare of forest territory.

Vivat to cross-spiders!

Sections: Biology

GOALS AND OBJECTIVES:

Spiders are one of the wonders of nature. Their diversity is amazing. About 35,000 species of spiders are known to science, but scientists believe that about the same number have not been described, so the total number should reach 70,000. Sizes vary greatly: from the smallest (0.8 mm) to the largest (11 cm). Spiders are one of the most common animals. The most rich in spiders are areas with abundant vegetation, but they are found in all landscape and climatic zones, from polar regions and high mountains to dry steppes and hot deserts. Spiders are found in Greenland near glaciers and on the Antarctic islands, many species are common in the mountains at an altitude of 2-3 thousand meters, and one species of horses was found on Everest at an altitude of 7 thousand meters. The habitats of spiders are extremely diverse. They live in the soil and on its surface, in the forest floor, in moss, on grassy and woody vegetation, under bark, in hollows, under stones, in rock crevices, in caves, in burrows and nests of other animals, in human dwellings.

Despite their significant role, spiders are very poorly covered in Russian bibliography, so the relevance of the topic is quite high, given the many blank spots. The scarcity of the material makes it necessary to take independent steps to study this topic. The conditions of summer holidays in central Russia provide such an opportunity. Research helps to understand the reasons for the prosperity of the spider family. Through observations, I aimed to better understand such issues as: the significance of the activity of spiders for the ecosystem, determining the main directions of aromorphoses, a deeper study of the structure of the external and internal, the dependence of the spider organism on the functions and instincts performed, the complexity of habits, distinctive features, establishing the causes of a wide distribution and survival. The secrets of such success should be sought in the specifics of the forms of biological behavior. There are forms such as food-procuring, defensive, construction and sexual. I will try to carry out their analysis and fulfillment of the tasks set on the basis of the signs of the orb-web spider Araneus diadematus , or Common cross .

GENERAL CHARACTERISTICS.

The common cross is one of the most typical spiders of the northern hemisphere. According to phenotypic features, the female is easily recognizable by a pale cross of white or yellow spots on the abdomen. The color of the abdomen is beige, darker than the rest of the color. The eyes form two rows, the legs are spiked, with light and dark transverse stripes. The male is smaller. Sizes vary: females - up to 18 mm, males - up to 9 mm. The main food is the liquid tissues of insects, which the spider catches with the help of a web. Distribution area - the spider is found in Europe, North America and most of Asia. Habitats - forests, bushes, roadsides and gardens. Adults can be found from June to November.

EVOLUTION.

Spiders are a very ancient detachment, known from Devonian and Carboniferous deposits, but already in those distant times, spiders were similar to modern ones, however, the most primitive ones. One can only say that the most characteristic feature of spiders - the arachnoid apparatus was formed by their ancestors in the very process of reaching land, and perhaps even in the water. Proof of this is spider warts. Indeed, in all chelicerates, when they land on land, the abdominal gill legs either turn into lungs and other special organs, or atrophy. Gill pedicels as such are unthinkable on land. Therefore, arachnoid warts could take shape only in aquatic or amphibious forms. They were formed in spiders from the legs of the tenth and eleventh segments, and the legs of the eighth and ninth turned into lungs. All this shows that spiders came to land in their own way, independently of other arachnids. Initially, the arachnoid apparatus was used for egg cocoons, as in those modern spiders, in which the arachnoid activity is still poorly developed in other respects. In the future, the web began to increasingly enter the life of spiders. The improvement of their organization was clearly manifested in the fact that initially the segmental ( metameric) organs are concentrated and begin to function as single systems (process oligomerization). The articulation of the abdomen disappears, and it becomes compact, the nervous system is highly concentrated, the number of segmental organs (spider warts, lungs, etc.) is reduced, while the rest take over entirely and enhance the corresponding functions. The coherence of the organism as a whole, the coordination and accuracy of movements, the speed of responses to the environment, etc. are growing. Higher spiders serve as clear evidence of these processes. Speaking about the phylogenetic development of the trapping webs of spiders, it should be mentioned that the evolution of the nets followed two independent paths. In one case, trapping nets arose from the cobweb lining of mink dens or pipes. At first, signal threads were stretched from the entrance, warning the spider about the approach of prey or an enemy. Then a funnel-shaped extension arose at the entrance, which gradually turned into a trapping net such as an awning or cloth. Another direction of development of the net, varied in results, is observed in spiders that have settled vegetation. They hung their cocoon from branches and leaves and initially guarded it, hanging nearby on a cobweb. The threads stretched from the cocoon served as signal. By adding new threads around the cocoon, an incorrect network was created. The next step is represented by the roof-like webs of spiders, whose horizontal canopy or dome of dense cobwebs was supported from above and below by vertical threads, bumping into which, the prey fell onto the canopy. The spider sits under the canopy, where the cocoon is also attached. From the arachnoid plexus with a cocoon in the center, the wheel-shaped webs of spiders of the families Araneidae, Tetragnathidae and Uloboridae, the most perfect type of nets, also originated. The stages of improvement in the organization of spiders are to a certain extent reflected in the now accepted division of the Aganei order into three suborders: lyphistiomorphic, or arthropod, spiders (Liphistiomorphae), mygalomorphic, or tarantulas in the broad sense (Mygalomorphae), and higher araneomorphic spiders (Araneomorphae), the last of which is the common cross. Previously, spiders were divided into four-lung (Tetrapneumones) and two-lung (Dipneumones), but this is less natural.

The branch of knowledge about spiders is called araniology. The order of spiders (Araneus) was isolated from among the arachnids by Clark in 1757 - in contrast to the classification of Linnaeus in 1735, which classified spiders as insects.
For a long time, Linnaeus's point of view, however, enjoyed predominant circulation, but the International Congress of 1948 restored the priority of Clark's classification.

The name of the class Arachnida comes from the Greek. arachne- spider. In ancient Greek mythology, Arachne was the name of a girl who was such a skilled weaver that, having challenged the very patroness of this craft, the goddess Athena, to a competition, she wove a fabric better than she. Annoyed, the goddess turned her rival into a spider, announcing that from now on Arachne and her entire family would spin and weave until the end of time.

ANATOMY.

outdoor structure . Spiders, unlike insects, do not have antennae (antennae) and jaws. The body is covered with an external skeleton ( exoskeleton) and consists of two sections - cephalothorax, formed by the merged head and chest, and abdomen. They are connected to each other by a narrow stem. The abdomen is non-segmented, its 11 segments are fused. The covers of this part are elastic, densely pubescent with hairs. At the anterior end of the cephalothorax are four pairs of simple eyes, the location of which serves as an important classification feature. Spider vision is imperfect. The front medial eyes, called the main ones, are dark; the rest, secondary eyes, usually shiny due to the inner shell (mirror) reflecting light. They form two transverse rows. The cephalothorax bears six pairs of limbs. In front of the head are two jaw-like 2-segmented chelicerae, each of which ends with a sharp claw. Poison glands located in these limbs open on it. Spider chelicerae pierce the integument of prey and inject venom and digestive juices into it. Unlike primitive spiders, whose chelicerae move in parallel and need to rise to capture prey, in higher ones they converge and diverge. Second pair - pedipalps, used as palps and grasping structures equipped with one claw. Their coxae are usually equipped with lobes that limit the preoral cavity and are covered with hairs that serve to strain liquid food. In mature males, their ends are modified and are used for mating. All spiders, unlike insects, have four rather than three pairs of walking legs. The last segment of each of them bears two comb-like claws, between which there is an unpaired appendage ( empodium), claw-shaped, or in the form of a sticky pad. Walking legs are adapted to perform different actions: the two front pairs control the movement, the third pair is shortened, serves as a support, the last pair unfolds and builds a web. All seven segments of the spider's leg move at different angles, and thanks to the soft shell in the joints, greater freedom of movement is achieved; leg muscles are attached to the inner walls. The integument consists of cuticle and hypodermis.

The sense organs play an important role in the life of a spider. The sense of touch is dominant. The trunk and appendages are covered with numerous tactile hairs and bristles, each of which is approached by a process of a sensitive nerve cell. The special structure of the hairs - trichobothria present on pedipalps and legs. There are up to 200 of them. With the help of trichobothria, the spider feels the most insignificant puffs of air, for example, from a flying fly. Trichobothria perceive rhythmic vibrations in a wide range of frequencies, but not directly as a sound, but through the vibration of the web threads, that is, as tactile sensations. They catch the slightest breath of air, it has been experimentally established that they perceive fluctuations in the atmosphere at a distance of up to a meter. Another kind of tactile sense is the perception of the degree of tension of the web threads. When their tension changes in the experiment, the spider seeks its shelter, always moving along the most tense threads. The organs of balance and hearing are unknown in spiders, but they have these senses. The olfactory organs are complex tarsal organs on the tarsi of the front legs. Spiders have chemoreceptors presented by lyre-shaped bodies. They are microscopic gaps in the exoskeleton, covered with a thin membrane, to which the end of the sensitive nerve fits. Some authors attribute to the lyre-shaped organs the functions mechanoreceptors, perceiving the tension of the exoskeleton, which allows you to adjust the degree of pressure on it. Spiders distinguish the smells of volatile substances, but usually react at a close distance from the source of the smell. For example, males distinguish the tenet of a sexually mature female from the tenet of an immature female by smell. The tarsal organs also serve as taste organs, with their help the spider in the experiment distinguishes between pure water and solutions of various substances. Sensitive taste cells are also found in the walls of the pharynx of spiders.

The arachnoid glands open on the underside of the abdomen with six arachnoid warts. In front of them are small respiratory openings - spiracles, or stigmas.

The spider is warm and moisture-loving. He, like many insects, is sensitive to changes in barometric pressure, which is why he is known as a “weather predictor”

Internal structure. The spider feeds on liquid tissues sucked from its victims, mainly insects. The digestive system of a spider consists of a mouth cavity, an expanding tube of the esophagus, which, passing through the brain, connects to a muscular organ called "sucking stomach". The sucking stomach is connected by a short tube to true stomach, to which, in turn, is attached intestine passing through the entire abdomen. A network forms in the abdomen thread-like organs ("liver"). The rectum ends with an anus that opens at the end of the body.

The circulatory system is an open, branching network of vessels ending directly in the tissues of the body, from where the blood, leaking, flows back into the vessels. The entire system is made up of the heart, arteries, veins, and spaces ( sinuses) between organs washed by gray-blue blood, hemolymph. Oxygen-carrying hemolymph pigment hemocyanin- contains copper just like human hemoglobin contains iron. Spider hemolymph also contains four types of cells - hemocytes, whose function has not yet been elucidated. A heart is a long tubular organ passing in the upper part along the center of the abdomen. It is enclosed in pericardium, a tubular chamber that covers the heart with elastic ligaments and organizes the circulation of hemolymph inside the circulatory system. The surface of the pericardium is covered with numerous nerve fibers, not only causing, but also directly regulating its reduction. The heart has four pairs of holes, ostius, along the entire length, working like valves through which the hemolymph moves under pressure in both directions. During contraction, it is directed in three directions - forward (through anterior aorta), back (through posterior aorta), as well as to the side. Small vessels, moving away from the posterior aorta, saturate the organs and tissues of the abdomen. The hemolymph entering the heart is directed by the pericardium through anterior aorta into the head. There through arterial vessels it, in turn, enters the organs and tissues. Further, gathering in the tissues, the hemolymph returns in the same way back to the abdomen, and enters the lungs. In the lungs, gas exchange occurs and, as a result, the hemolymph is saturated with oxygen, after which it flows back to the heart, where it accumulates in the pericardium and is then sent for further circulation. Unlike insects, the spider's heart is not divided into several chambers.

The spider breathes air. Their respiratory apparatus is interesting in that in this detachment there is a change of lungs by tracheas. This spider belongs to the two-lung, breathing pair of lungs and developed in place of the second pair of tracheae. There are tracheas of local and general significance. The former are represented by bundles of short, usually unbranched tubes that do not extend beyond the abdomen. The second ones are longer, sometimes anastomosing and branching, penetrating through the stalk of the abdomen into the cephalothorax and its limbs. There are also four non-branching tracheal trunks. The tracheae are relatively poorly developed, so pulmonary respiration still prevails.

The excretory system consists of a pair of coxal (coxal) glands in the cephalothorax and the so-called. malpighian vessels in the abdomen, which open into the intestines. The advantage of these vessels is that, in conditions of moisture deficiency, they retain all the moisture in the body of the spider, removing only excess salts and undigested products of digestion. Completely digested food accumulates in stercoral pocket bag-shaped, from where it is periodically removed through the anus.

The nervous system is similar to that of insects. It consists of the abdominal trunk with branches extending to different organs and ganglia, collected in the cephalothorax in a large subpharyngeal node, which has a star shape and performs basic motor functions. It controls the reflex and instinctive principles. Above it is supraesophageal- "brain", which receives information from the optic and other nerves. In addition, the brain has several glandular bodies, similar hypothalamus a person who secretes regulatory hormones. There are sensory hairs on the pedipalps and walking legs.

The reproductive organs are represented by the ovaries in females and the testes in males. The testicles are paired, convoluted spermatic tubes are connected near the genital opening, which in the male looks like a small gap. The ovaries are paired, in some cases fused at the ends into a ring. Paired oviducts are connected to an unpaired organ - the uterus, which opens with an oviduct. The latter is covered by a folded elevation - epigyna. There are seminal sacs - sacs from which tubules depart to the excretory part of the genital tract and to the epigyne, where they usually open independently of the oviduct. Aggregate organs are formed on the pedipalps of the male only during the last molt.

GROWTH.

Information. Spiders, like other arthropods, have a hard outer skeleton ( exoskeleton). In the process of growth, they have to shed their old covers ( shed). This spider has up to ten molts in its life. Dropped Spider Skin ( exuvium) is preserved so well that it can be mistaken for the body of an animal. In preparation for molting, the spider loses interest in food for a long time (usually for a week). During the linear stage, the spider hangs on a thread from its shelter or trapping net. Moulting begins with the fact that the dorsal shield rises, like an eyelid, and cracks appear on the sides of the abdomen. Removing the legs and pedipalps from the old skin is the most difficult procedure. If the leg cannot be retrieved, it may break, with the lost legs and pedipalps being regenerated during the next molt. During the shedding of old covers, spiders are defenseless and often die.

After shedding the old skin and before the new integuments harden, the body increases in size. At this moment, the spider takes in air so intensely that the new exoskeleton is free. At the same time, the proportions also change: the abdomen grows faster than the dorsal shield, therefore, at each next stage, the relative size of the abdomen is larger than at the previous one. The molting process in the later stages does not last longer than an hour. In total, the spider has to carry up to 10 lines. Males, which are smaller than females, also have fewer molts. During the last molt, the reproductive organs reach full development.

Study.

Date: 07/19/2007

Conditions: cloudy, warm

The following experiment was carried out: at 18:00, a female cross spider was found, preparing to molt. This was preceded by a long hunger strike, as the spider did not build a net for 8 days. Hanging on a cobweb attached to the substrate, emerging from the arachnoid warts, but not torn off from them, the individual hangs with its cephalothorax down. The process of getting rid of the former exoskeleton goes at different speeds. Quite quickly (5-6 minutes), the cover is shed from the abdomen and cephalothorax, while the limbs are released for more than 20 minutes. The whole complex operation takes about 40-45 minutes. I noticed the fact when the old skin is shed, soft tissues are lighter than before and devoid of pigmentation. Only after a while the color scheme returns. To speed up this process, the spider performs vigorous twitching of the limbs, which makes it possible to accelerate the flow of hemolymph, which, possibly, contributes to the return of the old color. Swaying in all directions from a light breeze, the spider resembles a plucked leaf, and given its pale protective color, we can talk about mimicry. Attention should be paid to the regeneration inherent in spiders during molting. In my opinion, this ability is of decisive importance, since it allows individuals to restore activity, which under other conditions would be doomed to death. During the experiment, I observed how the dropped exoskeleton remained hanging in place for a certain time and only then the spider unhooked it. I concluded: this is due to the fact that the former clothes are extremely similar to the spider itself, therefore, in cases of attack, it could serve as a distracting or misleading object. At 18:45, the investigated object returned to its lair, having previously waited for some time at the entrance in order to make sure that the covers were hard.

CONSTRUCTION ACTIVITIES.

Information. The construction activity of animals can be classified as tool. Such activity is typical primarily for invertebrates, in particular for spiders. The location of the net is very important: most often across the prevailing direction of flight of insects.

The ability to secrete a spider web is their characteristic feature. Spider web is a unique material that, despite its very small thickness, is extremely durable and elastic. The material for it is formed in special glands located in the back of the abdomen, and the so-called. arachnoid warts. At their ends there are numerous chitinous arachnoid tubes (modified hairs), which open the ducts of the arachnoid glands. The spider has three pairs of warts: two pairs of outer, 2-segmented, and a pair of posterior median, non-segmented. The spider glands are located in the abdominal cavity, in most cases they are well developed and numerous. The duct of each gland opens at the end of the arachnoid tube. Along with the usual tubules, there are a small number of so-called spider cones, on which the ducts of larger glands open. Spider warts have a total of more than 500 tubes and about 20 spider cones. The secret of the arachnoid glands is not squeezed out, but is pulled out by the back pair of legs and in the process of stretching it turns from a liquid into a solid thread.

There are up to five types of spider glands that produce webs for different purposes:

• Tree-like - a sticky secret on a trapping spiral;
• Pear-shaped - attaching radii to objects;
• Ampoule - spider web frame, inner radii, thickened threads;
• Lobular - the basis of the trapping spiral, wrapping prey, the inner layer of the cocoon;
• Tube-shaped - the outer layer of the cocoon.

The web is close in chemical composition to silkworm silk, from which it differs in a low content of an adhesive substance - with ericin, soluble in water. The basis of spider silk is the protein fibroin, formed by a complex complex of albumins, alanine and glutamic acid.

As the spider moves, it continuously sheds a web, which, like a climber does with a safety cable, it attaches from time to time to the surfaces it passes over. That is why a disturbed spider can almost always, with its legs crossed, fall from a support and, hanging on an tensile thread, descend along it to the ground.

Probably the most interesting feature of spiders is the construction of trapping webs from the web. Their forms are very diverse and the resulting construction may well serve as a taxonomic feature. Orb-weaving spiders from the family of crosses (Araneidae) build the most beautiful, so-called. wheel-shaped, shadow. First, the spider climbs to a high place, usually near a path or other open space, and secretes a very light thread, which is picked up by the breeze and, accidentally hitting a nearby branch or other support, is braided around it. The spider moves along this thread to a new point, along the way strengthening the web with an additionally secreted secret. In a similar way, two or three more relatively thick “cables” are laid, which make up a closed frame, inside which the trapping structure itself will be located. Usually the nets are oriented more or less vertically, but sometimes they come out with an inclination. Thread-radii are stretched between the sides of the frame, connecting in the center. Now, starting near this place, the spider moves towards the periphery in a spiral, leaving behind a thread attached to the radii, the distance between the coils of which is determined by the span of its limbs. While the web is not yet sticky, but having reached the outer frame, the spider again spirals, but with denser coils, returns back to the center, this time forming a thread, which, unlike the previous ones, is covered with droplets of sticky secretion. As this actually trapping spiral is laid, the thread of the first non-sticky spiral is bitten off and thrown away. Obviously, it served only as a kind of scaffolding. When the nets are ready, the spider moves to their center or, if it has reached a large size, to a shelter located next to the net and waits for some flying insect to stick to the web. If the author of a trapping net builds a shelter for himself, then a tightly stretched signal thread, so one leg always rests on it.

Study.

Location: north of the Kaluga region, Solnechny cooperative

Date and time: 06-07.08.2007, morning-evening

Conditions: no rain, sunny

The following experiment was carried out: at 21:50, a cross-spider was found emerging from its shelter. Exactly after the onset of the first sevens, the individual makes sure that the network is motionless, and after a positive response crawls out to the central plexus. By systematically twitching all the radial threads, the predator checks for the presence of arbitrarily large food. When such is found, he is taken to the meal, returning to the middle. While the spider is busy eating the accumulated prey, he will not start building a new web. Sometimes such cases were observed when the hunter spent the whole night on this occupation, as a result of which the next morning a new network was not built, and the spider was on a diet all day. Having finished with the last noteworthy victim, the spider begins to get rid of the old web, eating it along with small insects that have become entangled there during the day. Thus, we can conclude that the work is waste-free, since all the material spent on the web is returned for the most part back to the body. Depending on when the preliminary clearing of the old trapping net and its destruction was completed, the individual takes up the construction of a new one, which must be completed before dawn. Otherwise, if instinctive calculations do not allow him to meet, the cross is returned to the lair until the next night. The construction of the wheel-shaped web completely coincides with the above course of action. From this I concluded that, contrary to many sources, the time for building a network in the middle lane is not a day, but a night, which is associated with high daytime activity. The whole structure serves one day, and by the evening it is torn in many places, also losing its stickiness.

The very last and final step in the construction of the web is laying a tightly stretched signal thread leading to the lair. To verify its properties, I conducted the following experiment: at 15:00 I found a cross-spider, the signal thread of which went around a solid rock. Obeying its instincts, the spider is aware of the sound conductivity of the substrate, as it usually weaves webs on plants. But in this case, the vibrations are muffled and do not reach the owner of the web, as a result of which the spider remains in the dark about what is happening on the web. Not reacting to the hit, for example, of a blowfly, the orb-weaver gives it the opportunity to extricate itself. In other words, he has to be content with midges, which cannot fully satisfy the needs for food, and doom himself to a slow death from hunger. I also conducted another experiment: I hung a victim on the net, whose dimensions exceeded the cross. As a result, the hunter was able to react rationally due to too large amplitude of oscillations, remaining in the shelter. Thus, I concluded that from this thread, the spider can not only determine the fluctuations in the network, but also the location of the victim and even its size.

The following experiment was made: at 16:30, a young specimen of the cross was found, which had reached the third molt. She was busy building the network, and after the completion of construction, she remained in the middle, without conducting signal threads. It can be concluded that, unlike older counterparts, the young do not build a special den, being all the time on the central plexus. The signal thread is not carried out, perhaps in order to quickly overtake the entangled prey. Spiders grow quickly, so they need enough energy from food. It should be noted that the web was erected unusually early - in the middle of the day. Subsequent observations prove the correctness of the guess that young individuals do not have a pronounced biological clock that allows them to accurately orient their daily cycle. Only as they grow older, by the time of the sixth or seventh molt, the signs characteristic of the mature stage of development appear - the presence of a shelter, a signal thread, a biological clock. These signs may also be associated with puberty.

FOOD PRODUCTION ACTIVITIES.

Information . The food-procuring activity of a spider inevitably occupies the bulk of its daily activity. It is carried out through complex combinations of unconditioned and conditioned reflexes. According to the degree of forage specialization, this species is classified as stenophages due to the narrow specialization of the diet, as well as zoophagous like a carnivore. The main and secondary food is represented by various families of insects: dipterans, hymenoptera, lacewings, butterflies, less often - dragonflies and orthoptera. Nutrition is one of the permanent and individualized activities, therefore, when catching a prey, each individual maximizes the capabilities of its brain, which increases the efficiency of eating behavior.

Spiders are very voracious predators, feeding mainly on insects, which they suck. Prey is caught using complex trapping nets and neutralized, as a rule, with poison. The spider is characterized by large glands protruding into the cavity of the cephalothorax. Each of the two glands is surrounded by spiral muscles, during the contraction of which the poison is injected through the hole at the end of the claw-like segment of the chelicerae into the body of the victim. On small insects, the poison acts almost instantly, but larger ones continue to beat in the nets for some time. The prey is entangled in a web.

The filtering apparatus of the preoral cavity and pharynx, a narrow esophagus, a powerful sucking stomach - all these are adaptations for feeding liquid food. Having caught and killed the prey, the spider tears and kneads it with chelicerae, while pouring out the digestive juice that dissolves the internal tissues. The protruding liquid is absorbed, leaving the chitinous cover intact. The secretion of juice and the absorption of food droplets alternate, the spider turns the victim, processing it from different sides, until a wrinkled skin remains. In the digestion and excretion of spiders, the role of a large liver is essential, in the cells of which intracellular digestion of food and absorption take place. Part of the liver cells, overloaded with excretion, goes into the intestinal lumen and mixes in the cloaca with white secretions from the Malpighian vessels. Spiders do not need to store food, as their life cycle is limited to one annual season.

This species is quite harmless to humans, however, if handled carelessly, it can bite. The biological significance of spider venom comes down mainly to the killing of prey, so the poison is usually toxic to insects. According to the nature of the poisoning caused, spider venom is divided into two categories. The poison of some causes mainly local necrotic reactions, i.e., necrosis and destruction of the skin and deeper tissues in the bite area. The poison of others has a strong effect on the whole organism, in particular on the nervous system.

Study.

Location: north of the Kaluga region, Solnechny cooperative

Date and time: 08/05/2007, morning; 08/07/2007, noon

Conditions: cloudless, hot

The following experiment was set up: at 11:20 an elderberry (plant) was thrown into the web of a female cross. Reacting to it as if it were an ordinary victim, the spider began to absorb the nutritious juice from the core, after which it threw out the remaining shell. In my opinion, an irrefutable fact proving the conditionality of the division into zoophages and phytophages. The previous elderberry example would be an example of a random feed. Such an experiment was also carried out: at 15:00, a orb-web spider was seen carrying the caught prey to the lair. Before switching to the signal thread, the individual, by a sharp rise of the abdomen upwards, excreted excrement in small drops, which happens infrequently and only because of dense nutrition. I also note that during the absorption of food, the cobweb in which the victim was entwined was absorbed along the way.

On the example of numerous observations, it can be concluded that representatives of the families of Hymenoptera and Diptera (scavengers, meat eaters, hoverflies, horseflies, bees, bumblebees, wasps, etc.) form the basis of the diet of the cross. Despite the appetizing butterflies, they make up only a small fraction of the total catch. To prove this, I carried out several experiments. In the first, at 16:00, a hawk hawk was thrown into the spider's web. Since the hawk hawk is quite strong in order to escape, the spider instantly swoops down on the enemy. After a strong shaking and a short resistance, the predator neutralizes the opponent with one tenacious bite. To immobilize him, the hunter tightly wraps the victim with cobwebs and once again injects digestive juices with the poison. Since the scales of butterflies easily peel off and stick to objects upon contact, after contact with the hawk moth, the segments of the cross are clogged with them, due to which the owner of the web runs the risk of sticking to it. In order to prevent this from happening, he is forced to periodically moisten the tips of the paws with the secret of the oral glands. Only after such processing of the limbs, the spider is removed along with the prey to itself. Because the scales negate the stickiness of the web, the butterflies often manage to slip out of the web with strong flaps, which happened in the second experiment, which took place at 18:00. Since the trapping net is located high enough from the lower grass cover, grasshoppers rarely get to the cross for dinner. It should be noted that if the victim is large and the spider cannot cope with it, he frees it himself. It has been observed more than once how insects with a pungent odor are thrown out of the nets - bugs, lemongrass butterflies, certain types of hoverflies, etc. This fact is explained by the desire to keep the web in working condition for the rest of the day. Data on the species composition of the insects consumed by the cross can be summarized in a diagram:

SEXUAL ACTIVITY.

Information. During courtship, spiders exhibit surprisingly complex behavior. The male needs to come into contact with a female that is larger than him, and at the same time not be mistaken for a victim. Sexually mature males usually no longer build trapping nets, but wander in search of females and are caught on the female's nets during a short mating period. Often he has to travel considerable distances in search of a partner. In this case, the male is guided mainly by smell. He distinguishes the odorous trace of a sexually mature female on the substrate and her web. Having found the female, the male begins courtship. With characteristic movements, he twitches the threads of the female's web with his claws. The latter notices these signals and often rushes at the male as if it were prey, putting him to flight. Persistent "courtship", sometimes continuing for a very long time, makes the female less aggressive and prone to mating. The complex forms of male behavior are aimed at overcoming the predatory instincts of the female: the male behavior differs sharply from ordinary prey.

Before mating, the male releases a drop of sperm from the genital opening onto a specially woven spider mesh, fills it with sperm copulative organs of the pedipalps and, when mating, with their help, injects sperm into the female's seminal receptacles. On the foot of the pedipalp there is a pear-shaped appendage - bulbus with a spiral spermatic canal inside. The appendage is extended into a thin spout - embolus, at the end of which the channel opens. During mating, the embolus is inserted into the tubule of the female's seminal receptacle. The pedipalps of the male and the genital opening of the female in each species fit together like a key to a lock.

Eggs are laid a few days or weeks after mating. Fertilization occurs in the uterus, with which the seminal receptacles communicate. The masonry is placed in a cocoon made of cobwebs. Usually the female turns her lair into a nest in which eggs are laid and a cocoon is woven. As a rule, the cocoon consists of two gossamer plates, fastened with edges. First, the female weaves the main plate, on which she lays her eggs, and then braids them with the cover plate. These lenticular cocoons are attached to the substrate or wall of the nest. The walls of the cocoon are sometimes impregnated with a secret secreted through the mouth. The cocoon is spherical, its tissue is loose and fluffy, resembling delicate cotton wool. One cocoon is laid, it contains up to 600 eggs. For some time the female guards the cocoon in nets. The instinct to protect offspring is the weaker, the more reliable the shelter is.

Hatching of juveniles from eggs of the same clutch occurs more or less simultaneously. Before hatching, the embryo is covered with a thin cuticle, spines are formed at the base of the pedipalps - “facial teeth”, with the help of which the facial membranes are torn. The hatched spider has thin covers, undivided appendages, is immobile and cannot actively feed. He lives off the yolk that remains in the intestines. During this yolk period of development, which varies in duration, the juveniles remain in the cocoon and molt. The first molt occurs while still in the egg, so the molted skin is shed along with the facial membranes at hatching. Becoming more active, the spiders emerge from the cocoon, but usually they still stay together for some time. If you touch such a cluster, in which sometimes there are several hundred spiderlings, they scatter along the web of the nest, but then again gather in a dense club. Soon the spiders disperse and begin to live on their own. It is at this time that the juveniles are resettled on cobwebs through the air. Young spiders climb onto towering objects and, raising the end of the abdomen, release a web thread. With a sufficient length of the thread, carried away by air currents, the spider leaves the substrate and is carried away on it. Settling of juveniles usually occurs in spring. Spiders can be lifted by air currents to considerable heights and transported over long distances. There are known cases of the mass appearance of spiders flying onto ships hundreds of kilometers from the coast. Settled small spiders are similar in structure and lifestyle to adults. They settle in habitats characteristic of each species and, as a rule, from the very beginning arrange dens or weave trapping nets, which are typical for the species in design, only increasing them as they grow. The life cycle ends within a year. Sexual maturity is reached at the end of summer, and after laying eggs, adult spiders die. In this case, an autumn-winter diapause is often observed, the development of eggs stops in autumn, despite the fact that it is still quite warm in nature, and resumes only next spring.

Study.

Location: north of the Kaluga region, Solnechny cooperative

Date and time: 12.07.2007, 07-08.08.2007, day

Conditions: clear, sunny

The following experiment was carried out: at 15:30 a male cross-spider was found. In its external coloration, the male, which is smaller, turned out, contrary to many sources, to be completely identical to that of the female. This individual, having found the net of a potential partner, performed complex rituals in the form of twitching threads for quite a long time for half an hour. Having approached the very den of the female, the male began to act even more cautiously. The female reacted to the appeals of the male, but, without even coming close, she rejected the newly-born groom. This fact once again proves the chemical nature of the relationship between spiders, the males of which distinguish fertilized females at a distance. At 16:20 the male finally left the web of the female. The second experience turned out to be interesting: a complete repetition of the first, but with more sad consequences. The same male spider lands on the female's web a second time the next day at 18:00. Having endured the intruder once, the female did not give him a second chance to retreat. Thus, I became a witness to a fairly common phenomenon of cannibalism, especially where the difference between adults is more than 2 times. In this case, a lump of the digested remains of a male was found in the jaws of the female in the morning. In reality, the males try to bypass those lairs where they have already visited, but it turned out to be much easier to disorientate them. This case once again confirms the aggressive nature of females, both against enemies and against males.

Another observation is also curious: in the interval between dangerous visits to partners, the male is deprived of his livelihood in the form of a web. However, even here they found an original way out of the situation: in order not to die of hunger, the male climbs some kind of elevation at night, descends on the thread and hangs down on it with his cephalothorax. With its front legs wide apart, it stretches a small trapping net, catching flying insects with instantaneous movements, like its distant illustrious relative Deinopis. Therefore, we can conclude that the species has a variety of methods for catching prey: not only passive, but also active. I also made another experiment: at 13:00, many small newborn spiderlings were separated and scattered in different plant bushes. As a result, after a few hours, the young began to gather in separate small clusters, thus imitating the original large nest. It can be noted that the instinct of self-preservation is manifested: even disunited, they try to endure the danger together. There is another explanation: juveniles huddle together in dense clusters in order to maintain a constant, higher temperature.

DEFENSIVE ACTIVITIES.

Information . Spiders have two main forms of defensive reactions: active defensive and passive defensive. Passive-defensive reaction manifests itself in the form of fear of irritants - inedible insects in nets. An active-defensive reaction is expressed in the form of aggression directed at representatives of one's own (during courtship) or another species (during hunting). It should be noted that with representatives of their own species, i.e. with competitors, they get along calmly even in a small area.

Being predators, spiders undoubtedly play the role of population regulators, primarily insects, in natural communities of organisms - biocenoses. At the same time, spiders themselves serve as food for various animals. Spiders feed on small mammals and birds. The main enemies of spiders are wasps of the families Pompilidae and Sphecidae. They fearlessly attack them in the nets. With a sting in the nerve centers, the wasp paralyzes the spider without killing it, and then drags it into its hole. An egg is laid on the body of the prey, the emerging larva feeds on the spider as “live canned food”.

In addition to the poisonous apparatus, cryptic(protective) coloring and a hidden lifestyle, the spider has reflex defensive reactions. The latter are expressed in the fact that, being disturbed, the spider falls to the ground on a cobweb that connects it with the nets, or, remaining on the net, produces such rapid oscillatory movements that the contours of the body become indistinguishable. For adults, a threat posture is characteristic - the cephalothorax and protruding legs rise towards the enemy, as well as jerky movements. The intricate pattern of the abdomen is explained by the fact that the spider lives among plants in conditions of alternating light and shade.

Study .

Location: north of the Kaluga region, Solnechny cooperative

Date and time: 11-18.07.2007

Conditions: cloudy, warm

The following experiment was carried out: at 17:00, a pelops wasp and a cross-spider paralyzed by it were found. Naturally, having driven the killer away from the unfortunate victim, I undertook to cure the spider. To do this, I needed to transfer the patient to a warm room and every hour to carefully carry out “gymnastics” with him, alternately moving the limbs. A day later, weak reactions appeared, and after 4 days the ward himself was able to escape. This suggests that the method I used to treat a paralyzed person worked in the case of a lower organism, and the course of the disease is also similar. It was also empirically established how it is easy to distinguish a dead spider from a living one: in the first eye, under normal conditions, dark ones turn white, which is associated with a cessation of the flow of hemolymph and nutrients there. When confronting an attacker, the spider always tries to protect the most vulnerable part of the body from defeat - the abdomen, which is not protected by hard covers.

INSTINCT OR MIND.

Information. All of the above shows how highly developed spider instincts are. The latter, as is well known, are unconditioned reflexes, that is, complex innate reactions of the animal to changes in the external and internal environment. A tiny spider, recently hatched from an egg, immediately builds a trapping net in all the details characteristic of this species, and makes it no worse than an adult, only in miniature. However, the instinctive activity of spiders, with all its constancy, cannot be considered absolutely unchanged. On the one hand, spiders develop new reactions in the form of conditioned reflexes to certain external influences. On the other hand, the chains of instincts themselves, the order of individual acts of behavior, can vary within certain limits. For example, if a spider is removed from the net before the completion of its construction and another spider of the same species and age is planted on it, then the latter continues to work from the stage at which it was interrupted, i.e., the entire initial stage in the chain of instinctive acts, as it were disappears. When individual pairs of limbs are removed from the spider, the remaining pairs perform the functions of the removed ones, the coordination of movements is restructured, and the network design is preserved. These and similar experiments are interpreted by some zoopsychologists as a refutation of the unconditioned reflex nature of the behavior of spiders, up to attributing intelligent activity to spiders. In fact, there is a plasticity of instincts here, developed in spiders as an adaptation to certain situations that are not uncommon in their life. For example, a spider often has to repair and supplement its web, which makes understandable the behavior of a spider on someone else's incomplete web. Without the plasticity of instincts, the evolution of arachnoid activity is unthinkable, since in this case there would be no material for natural selection.

Study .

Location: north of the Kaluga region, Solnechny cooperative

Date and time: 06-07.08.2007, morning-afternoon

Conditions: cloudy, warm

Several examples can be cited to confirm the plasticity of reflections.

At 18:00, a cross-spider was found that built a web in the pattern of a wooden gazebo and stretched a signal thread around a metal pole. Since the vibrations were dampened, for several days the spider received scanty prey. After several coercive ejections by the employee into the web with prey, the spider began to lead the signal thread to the pole, and the web has functioned normally since then.

In another experiment, at 11:30 a.m., a stalk-shaped stimulus was brought to the spider. At first, the cross immediately retreated or assumed a threatening pose, but after repeated repetition and a safe outcome, it began to ignore touches within acceptable limits. In my opinion, further evolution can take the path of improving skills and developing more complex skills, including the complication of the structure of higher nerve ganglions.

PRACTICAL APPLICATION OF THE ROUND-SWITCH WEB.

Information. This material is unique in many ways. For example, a web is three times stronger than steel of the same diameter. The average thickness of the web thread is 0.0001 mm. In terms of physical properties, it is close to caterpillar silk, but much more elastic and stronger. The breaking load for cobwebs is from 40 to 200 kg per 1 mm of thread section, while for caterpillar silk it is only 33-43 kg per 1 mm. Attempts to make fabric from cobwebs have been made since ancient times. Exceptional in terms of strength, lightness and beauty, web fabric is known in China under the name “fabrics of the eastern sea”. Polynesians used the web of large web spiders as thread for sewing and weaving fishing gear. At the beginning of the 18th century in France, gloves and stockings were made from the web of crosses, presented to the Academy of Sciences and aroused universal admiration. It is known that the thread can be wound onto a spool directly from the spider web warts of the cross, enclosed in a small cell, and from one spider immediately up to 500 m of thread is obtained. The production of spider silk invariably faces the difficulty of mass breeding of spiders, primarily feeding these predators. Moreover, to quickly obtain one kilogram of fiber, more than 1.3 million spiders are required! It is possible that the development of artificial nutrient media will solve this problem, especially since artificial feeding of silkworm caterpillars is already practiced in Japan. While the web is used in optics for the manufacture of sights (crossing threads) in the eyepieces of various devices.

Reasoning.

I believe that the area of ​​possible application of the web is much wider. It seems possible to build special spider farms, which would grow a bred breed of spiders that produce a precious substance in large quantities. One can hope for the development of genetics, which will allow to implant some of the genes responsible for the secretion of the web in an animal that is more suitable for breeding. Web-woven materials, like a biopolymer, can be compared in reliability to any other known fiber. Indeed, in nature, all types of products have long been created, having perceived which mankind is able to more deeply master the world around us. On an astronomical scale, the web is exactly that product.

GALLERY.

Bibliography:

1. Hilliard P. (2001) Spiders. Moscow: Astrel
2. Sterry P. (1997) Spiders. Moscow: Belfast
3. Kozlov M., Dolnik V. (2000) Crustaceans and arachnids. Moscow: MGU Publishing House
4. Collection "Tree of knowledge"(2001-2007), volume "Animals and plants". Moscow: Marshall Cavendish
5. Encyclopedia Around the World. http://www.krugosvet.ru/
6. Encyclopedia Wikipedia. http://www.wikipedia.com/
7. Veterinary portal "Avicenna". http://www.vivavet.ru/

Class Arachnida (Arachnida)

Arachnids are terrestrial chelicerates with a large cephalothorax bearing short claw-shaped or claw-shaped chelicerae, long pedipalps, and four pairs of long walking legs. The abdomen is devoid of limbs. Breathe through lungs or trachea. In addition to the coxal glands characteristic of aquatic forms, they have Malpighian vessels.

For many arachnids, the secretion of arachnoid filaments from special arachnoid glands is characteristic. The web plays a significant role in the life of arachnids: in the extraction of food, protection from enemies, resettlement of juveniles, etc.

The Latin name of the arachnids Arachnida is given by the name of the heroine of the myths of Ancient Greece - the needlewoman Arachne, who was turned into a spider by Athena.

External structure. Arachnids are extremely diverse in body shape and size, segmentation, and limb structure. They differ from primary aquatic chelicerae in adaptations to life on land. They have thinner chitinous covers, which lightens the weight of their body, which is important for land animals. In addition, as part of the chitinous cuticle, they have a special outer layer - the epicuticle, which protects the body from drying out. In arachnids, the gill legs on the abdomen have disappeared, and instead, air-respiratory organs, lungs or tracheas, have appeared. The rudiments of the abdominal legs in them perform sexual, respiratory functions or have turned into arachnoid warts. The walking legs of arachnids are longer than those of aquatic chelicerae and are adapted for movement on land.

Within the class of arachnids, oligomerization of body segmentation is observed until the complete fusion of all segments. There are several types of body dissection in arachnids, the most important of which are as follows.

The scorpions, similar in external morphology to fossil crustacean scorpions, are characterized by the greatest dissection of the body (Fig. 295). The cephalothorax of scorpions, like most chelicerae,

fused and consists of an acron and seven segments, of which the last segment is reduced. The abdomen is subdivided into the anterior abdomen of six wide segments and the posterior abdomen of six narrow segments and a telson with a poisonous needle.

Solputas have a more primitive division of the cephalothorax than other arachnids: the acron and the first four segments are fused, while the last three segments are free, of which the very last segment is rudimentary. A similar dismemberment is observed in some ticks.

The harvestmen have a fused cephalothorax, and the abdomen consists of nine segments and a telson, which is fused with the last abdominal segment. The abdominal region is no longer subdivided into the anterior and posterior abdomen. A similar dismemberment is also characteristic of haymaking mites.

Rice. 295. Scorpion Buthus eupeus: A - view from the dorsal side and B - from the ventral side (according to Byalynitsky-Birula); VIII-XIX - abdominal segments; 1 - cephalothorax, 2 - chelicerae, 3 - pedipalp, 4 - leg, 5 - telson, 6 - poisonous needle, 7 - posterior abdomen, 8 - anterior abdomen, 9 - anus, 10 - pulmonary fissures, 11 - comb organs, 12 - sex caps

Spiders have a fused cephalothorax and abdomen. Due to the seventh segment of the cephalothorax, a constriction is formed between the cephalothorax and abdomen. The abdomen is formed by 11 fused segments and a telson.

The body of most ticks is completely fused.

The limbs of arachnids are diverse in form and function. Chelicerae are functionally similar to crayfish mandibles. These organs serve to crush food or bite through the victim. They can be claw-like, like in scorpions, salpug, or claw-like, like in spiders, or stiletto-like, like in many ticks. Pedipalps may serve to capture or hold prey. Grasping pedipalps with a claw at the end are characteristic of scorpions and false scorpions. Salpug pedipalps are flagellate and perform a sensory function. In spiders, pedipalps are similar to the mouth tentacles of insects. Tactile, olfactory sensilla are concentrated on them. In males of many spiders, copulatory organs are located on the pedipalps. In some ticks, pedipalps, together with chelicerae, are part of the piercing-sucking mouthparts. The four pairs of walking legs in all arachnids consist of 6-7 segments and are used for locomotion. In solpugs, telifons, the first pair of walking legs performs the function of sensory organs. There are many tactile hairs on the legs of arachnids, which compensates for their lack of antennae characteristic of other arthropods.

On the abdominal region of some arachnids there are rudiments of limbs that perform various functions. So, in scorpions, on the first segment of the abdomen, there are paired genital opercula covering the genital openings, on the second, special sensory comb-like organs, and on segments 3-6 m, lungs - modified gill legs. Spiders on the underside of the abdomen have 1-2 pairs of lungs and 2-3 pairs of appendages - arachnoid warts, which are modified rudiments of limbs. Some lower ticks have three pairs of coxal organs on their abdomens, which are appendages of coxae (coxae) of reduced legs.

The integument is represented by skin - the hypodermis, which secretes a chitinous cuticle, consisting of two or three layers. The epicuticle is well developed in spiders and harvestmen, as well as in some mites. The cuticle of many arachnids glows in the dark, due to the special structure of chitin, which polarizes transmitted light. Skin derivatives include poisonous glands at the base of chelicerae in spiders and a poisonous needle in scorpions, spider glands of spiders, pseudoscorpions, and some mites.

Internal structure. The digestive system of arachnids consists of three sections (Fig. 296). Depending on the type of food, the structure

intestine varies. A particularly complex structure of the digestive system is observed in predatory arachnids with extraintestinal digestion. This way of feeding is especially characteristic of spiders. They pierce the victim with chelicerae, inject poison and digestive juices of the salivary glands and liver into the victim. Under the influence of proteolytic enzymes, the tissues of the victim are digested. Then the spider sucks in half-digested food, and only covers remain from the victim. On the web of a spider, you can often see the covers of insects sucked out by it.

In the structure of the intestines of spiders, there are a number of adaptations to this method of nutrition. The foregut, lined with a cuticle, consists of a muscular pharynx, esophagus, and sucking stomach. Due to the contraction of the muscles of the pharynx and especially the stomach, the spider absorbs liquid semi-digested food. The middle intestine in the cephalothorax forms blind processes (in spiders - five pairs). This allows spiders and other arachnids to ingest large volumes of liquid food. The middle intestine in the abdominal region forms paired glandular protrusions - the liver. The liver functions not only as a digestive gland, phagocytosis occurs in it - intracellular digestion. Spiders have four pairs of liver appendages. The posterior part of the midgut forms a swelling into which the excretory tubules of the Malpighian vessels empty. Excrements and excretions are formed here, which are then excreted through the short hindgut to the outside. Arachnids can starve for a long time, as they form reserves of nutrients in a special spare tissue - the fatty body located in the mixocele.

Rice. 296. Scheme of the internal structure of a spider (neg. Aranei) (from Averintsev): 1 - eyes, 2 - poisonous gland, 3 - chelicera, 4 - brain, 5 - mouth, 6 - subesophageal ganglion, 7 - outgrowths of the middle intestine, 8 - base of walking legs, 9 - lung, 10 - spiracle, 11 - oviduct, 12 - ovary, 13 - arachnoid glands, 14 - arachnoid warts, 15 - anus, 16 - Malpighian vessels, 17 - ostia, 18 - liver ducts, 79 - heart, 20 - throat

excretory system. The excretory organs are represented by coxal glands and malpighian vessels. There are 1-2 pairs of coxal glands in the cephalothorax, which correspond to the coelomoducts. The glands consist of a mesodermal glandular sac, from which a convoluted canal departs, passing into a direct excretory canal. The excretory openings open at the base of the coxae of the third or fifth pairs of limbs. Coxa, or coxa, is the basal segment of the legs of arthropods. The position of the excretory glands near cox walking legs was the basis for their name - coxal. In embryogenesis, the coxal glands are laid down in all arachnids, but in adult animals they are often underdeveloped.

Malpighian vessels are special excretory organs characteristic of land arthropods. In arachnids, they are of endodermal origin and open into the posterior midgut. Malpighian vessels secrete excretions - grains of guanine. In the intestines, moisture is drawn from the excreta, which saves water loss in the body.

Respiratory system. Arachnids developed two types of respiratory organs: lungs and tracheas. There is a hypothesis that the lungs of arachnids were formed from the abdominal gill legs of crustaceans. This is evidenced by their lamellar structure. So, in scorpions, the lungs are located on 3-6 m segments of the abdomen and are deep protrusions, in which there are thin pinnate leaves from the inside. In their structure, the lungs of arachnids are similar to the gill legs of aquatic chelicerae, immersed in skin cavities (Fig. 297). Lungs are also found in flagellates (two pairs) and spiders (1-2 pairs).

The trachea are also the organs of air respiration in land chelicerae. They are skin invaginations in the form of thin tubules. Probably, tracheae arose independently in different phylogenetic lineages of arachnids. This is evidenced by the different arrangement of stigmas (breathing holes) in different arachnids: in most - on the 1st-2nd segments of the abdomen, in salpugs - on the 2nd-3rd segments of the abdomen and on the cephalothorax and an unpaired stigma on the fourth segment of the abdomen, in two-lungs spiders - on the last segments of the abdomen, and in some - at the base of chelicerae or walking legs or at the site of reduced lungs. The most powerfully developed tracheal system in salpugs, in which longitudinal trunks and branches are distinguished, passing into different parts of the body (Fig. 298).

Different orders of arachnids have different respiratory organs. Only pulmonary respiration is characteristic of scorpions, flagellated and four-lung spiders. Tracheal breathing is characteristic of most arachnids: pseudoscorpions, salpugs, haymakers, ticks and some

spiders. Bi-lung spiders have one pair of lungs and one pair of windpipes. Some small ticks do not have respiratory organs and breathe through the skin.

Circulatory system open. The heart is on the dorsal side of the abdominal region. In arachnids with a pronounced dismemberment of the body, the heart is long, tubular with a large number of awns; for example, scorpions have seven pairs of ostia, while in other arachnids the heart shortens and the number of ostia decreases. So, spiders have a heart with 3-4 pairs of ostia, and ticks have one pair. Some small ticks have a reduced heart.

Nervous system. The brain consists of two sections: the protocerebrum, which innervates the eyes, and the tritocerebrum, which innervates the chelicerae (Fig. 299). The deutocerebrum, characteristic of other arthropods that have the first pair of antennae, is absent in arachnids.

The ventral nerve cord innervates the remaining limbs of the cephalothorax and abdomen. In arachnids, there is a tendency for the ganglia of the ventral nerve cord to fuse (oligomerization). The most dissected forms, like scorpions, have one fused cephalothoracic ganglion and seven ganglia in the abdominal region. In salpugs, in addition to the cephalothoracic ganglion, there is only one abdominal node; in spiders, only the cephalothoracic ganglion is preserved, while in ticks and harvestmen, only the peripharyngeal ganglionic accumulation is expressed.

sense organs. The organs of vision are poorly developed and are represented by 1, 3, 4, b pairs of simple ocelli on the cephalothorax. Spiders often have eight eyes arranged in two arcs, while scorpions have one pair of large median ocelli and 2-5 pairs of lateral ones.

The main sense organs in arachnids are not eyes, but tactile hairs and trichobothria, which detect air vibrations. Some arachnids have chemical sense organs - lyre-shaped organs. They are small gaps in the cuticle, at the bottom of which sensory processes of nerve cells fit in a soft membrane.

Most arachnids are predators that hunt in the dark, and therefore the organs of touch, seismic sense (trichobothria), and smell are of particular importance for them.

reproductive system. Spider-like dioecious (Fig. 300). Some show sexual dimorphism. In many spiders, males are slightly smaller than females, and they have swellings on their pedipalps - seminal capsules, which they fill with sperm during the breeding season.

Gonads paired or fused. The ducts are always paired, but may flow into an unpaired canal, which opens with a genital opening on the first segment of the abdomen. Males of some species have additional glands, while females have seminal receptacles.

Rice. 300. Reproductive system of arachnids (from Lang): male reproductive system (A - scorpion, B - salpuga); female reproductive system (B - scorpion, G - spider); 1 - testis, 2 - vas deferens, 3 - seminal vesicle, 4 - additional glands, 5 - ovary, 6 - oviduct

Reproduction and development. Fertilization in arachnids can be external-internal or internal. In the first case, males leave spermatophores - packages of sperm on the soil surface, and females find them and capture them with the genital opening. Males of some species insert spermatophores into the genital opening of females with the help of pedipalps, while others initially collect sperm in seed capsules on pedipalps (Fig. 301), and then squeeze it into the genital tract of females. Some arachnids are characterized by copulation and internal fertilization.

The development is direct. Eggs hatch into juveniles that look like adults. In some species, eggs develop in the genital tract, and live births are observed (scorpions, pseudoscorpions, some ticks). Metamorphosis is often observed in ticks, and their nymph larvae have three pairs of walking legs, and not four, as in adults.

The arachnid class is subdivided into many orders, of which we will consider the most important: the Scorpion detachment (Scorpiones), the Zhgutopodye detachment (Uropygi), the Solpugi detachment (Solifugae), the Pseudoscorpiones detachment, the Haymakers detachment (Opiliones), the Spider detachment (Aranei) and detachments ticks: Acariformes, Parasitiformes, Opiliocarina (representatives of the orders are shown in Figure 302).

Order of Scorpions (Scorpiones). These are the most ancient arachnids. There are paleontological findings that testify to their origin from aquatic crustacean scorpions. Land scorpions have been known since the Carboniferous.

The scorpion order is characterized by the greatest dismemberment of the body. The fused cephalothorax is followed by six segments of the anterior abdomen and six segments of the posterior abdomen (Fig. 295). The telson forms a characteristic swelling with a poisonous needle. Chelicerae are claw-shaped, closing in a horizontal plane. Pedipalps are prehensile with large claws. Walking legs end in a paw with two claws. Scorpions on all segments of the anterior abdomen have derivatives of the limbs: on the first - paired genital caps, on the second - comb-shaped organs, on the 3rd-6th - lungs, opening with four pairs of respiratory openings (stigmas).

Scorpions live in countries with a warm climate. These are nocturnal predators, hunting mainly for insects, which are grabbed by pedipalps and sting with a needle. They are characterized by live birth and care for offspring. For some time, the female carries her offspring on her back, throwing her back with a poisonous needle on her back.

About 600 species of scorpions are known. The most widely distributed in the Crimea, the Caucasus and Central Asia is the motley scorpion (Buthus eupeus). Scorpion stings in most cases are not dangerous to humans.

Detachment Bitelegs, or Telifones (Uropygi). Telifon - a tropical group of arachnids, including only 70 species. These are relatively large arachnids, up to 7.5 cm long. In Russia, only one species of telephons (Telyphonus amurensis) is found in the Ussuri region.

The main morphological characteristic of telephons is that their first pair of walking legs has turned into long sensory appendages, and many of them have a special long caudal filament, divided into small segments (Fig. 302, B). This is a feeling organ. Chelicerae with claw-like segment, pedipalps claw-shaped. The seventh segment of the cephalothorax forms a constriction on the border with the abdomen. Abdomen 10-segmented, not subdivided into anterior metabelly.

Telifons are nocturnal predators and navigate in space mainly due to the organs of touch and seismic sense located on elongated sensory limbs. Hence the name - teliphones, as they hear the approach of a victim or enemy at a great distance by rustling or weak wave vibrations of the air.

The phones breathe with lungs. They have two pairs of lungs located on the 8th-9th segments. Fertilization is spermatophoric. They lay eggs. The female takes care of the young, carrying them on her back. They have protective anal glands. When threatened, they spray a caustic liquid from the anal glands.

Order Solpuga (Solifugae). Salpugs, or phalanxes, are a detachment of large arachnids that live in steppes and deserts. In total, about 600 species are known. The cephalothorax of the salpug is unfused and consists of a protopeltidia - the head section (acron and 4 segments) and three free segments, of which the last is underdeveloped (Fig. 302, A). The abdomen is 10-segmented. Powerful chelicerae are claw-shaped and close in a vertical plane. Pedipalps are similar to walking legs, they are involved in locomotion and also perform a sensory function. Breathe with trachea. The main tracheal trunks open with paired spiracles on the second and third abdominal segments. In addition, there is an unpaired spiracle on the fourth segment and a pair of additional spiracles on the cephalothorax. Salpugs are not poisonous. They feed mainly on insects. They hunt at night. The most common species is Galeodes araneoides (Crimea, Caucasus) up to 5 cm long. Fertilization is spermatophoric. The eggs are laid in a burrow. The female takes care of the offspring.

Squad Pseudoscorpiones. These are small arachnids (1-7 mm) with large claw-shaped pedipalps and therefore resemble scorpions. Their cephalothorax is fused, and the abdomen is 11-segmented, not divided into anterior and posterior abdomen. The ducts of the spider glands open on the claw-shaped chelicerae. Tracheal stigmas open on the 2nd or 3rd segments of the abdomen.

False scorpions live in the forest floor, under the bark, and also in human dwellings. They are small carnivores that feed on small mites and insects. Fertilization is spermatophoric. The male lays a spermatophore with two horns, and the female crawls onto the spermatophore and inserts its horns into the openings of the seed receptacles. The female lays fertilized eggs in a special brood chamber on the ventral side of the body. The larvae emerging from the eggs are suspended from the bottom of the brood chamber and feed on the yolk secreted from the female's ovaries into her brood chamber.

About 1300 species of false scorpions are known. Book false scorpion (Chelifer cancroides) is not uncommon in houses (Fig. 302, B). Its appearance in book depositories indicates that the mode of storing books has been violated. False scorpions usually appear in damp rooms, where favorable conditions are formed for the development of small insects and ticks - pests of books.

Order Haymakers (Opiliones). This is a large, widespread group of arachnids that look like spiders. Harvestmen differ from spiders in the absence of a constriction between the cephalothorax and abdomen, the articulation of the abdominal region (ten segments) and claw-shaped, rather than hook-shaped, like in spiders, chelicerae. A total of 2500 species are known.

Harvestmen are found everywhere on the surface of the soil, in cracks in the bark of trees, on the walls of houses and fences. They feed on small insects and hunt at night. Breathing is tracheal. There is one pair of stigmas on the first segment of the abdomen on the sides of the genital shield. They are characterized by the ability to autotomy, or self-mutilation. Lost legs are not restored. A predator can only grab a haymaker by the leg, which then breaks off, which saves the haymaker's life. The severed leg of the haymaker twitches convulsively for a long time and resembles a scythe in shape. Therefore, they are often called "spider-hay-mow" or "mow-mow-leg". The legs of the harvesters are climbing, with a multi-segmented tarsus.

Haymakers do not secrete cobwebs and actively hunt for their prey themselves. They play a positive role in reducing the number of insects. On the soil surface and in the grass layer, the density of hayfields often reaches several tens per 1 m2. The most common haymaker (Phalangium opilio, Fig. 302, D), which is found in various natural landscapes and even in cities. The body is brownish, up to 9 mm long, and the legs are up to 54 mm.

Detachment Spiders (Aranei). Spiders are the largest order of arachnids, including more than 27 thousand species. Morphologically, they are well distinguished from other orders. Their body is clearly divided into a fused cephalothorax and a fused rounded abdomen, between which there is

constriction formed by the seventh segment of the cephalothorax. Their chelicerae are hook-shaped, with ducts of poisonous glands. The pedipalps are short, tentacle-shaped. Four pairs of walking legs often end in comb-like claws that serve to stretch the web. On the underside of the abdomen are arachnoid warts. Eyes (usually eight) are located on the cephalothorax. Most spiders (two-lung suborder) have one pair of lungs and a pair of tracheae, and some tropical spiders (four-lung suborder) have only lungs (two pairs).

The web is important in the life of spiders. The complex behavior of spiders in connection with the use of the web at all stages of the life cycle determined their wide ecological radiation and flourishing.

From the web, spiders build their dwelling between leaves, branches or in a soil hole. The cobweb envelops the oviposition of spiders with the formation of an egg cocoon. Often, female spiders wear a cocoon under their abdomen, taking care of their offspring. Small spiders secrete a long cobweb thread, which is picked up by the wind, carrying the spiders over long distances. This is how the species spreads. The web is used to catch prey. Many spiders build a trapping web (Fig. 303, 1). Even mating behavior is not complete in spiders without a web. During the breeding season, male spiders make a web "hammock" into which they release a drop of sperm. The male then crawls under the hammock and fills his seminal pods on the pedipalps with sperm. Seed capsules play the role of copulatory organs, with the help of which the spider injects sperm into the female genital opening.

Only two-lung spiders live on the territory of our country, about 1500 species. The most characteristic representatives among spiders are: house spider (Tegenaria domestica), cross spider (Aganeus diadematus, Fig. 303), tarantula (Lycosa singoriensis), silver spider (Argyroneta aduatica).

The house spider lives in a human dwelling and stretches horizontal cobwebs in which it catches flies and other insects. The cross spider is a larger species, with a distinctive white cross pattern on its abdomen. Its vertically stretched nets can be seen on the walls of houses, fences, between tree branches. The house spider and the cross are spiders that build nets - a trapping net in which prey is entangled.

A special group of spiders is formed by wolf spiders, which pursue prey on the go. They find shelter in special minks dug in the ground and lined with cobwebs. They have long legs and a narrow abdomen. These spiders include a tarantula that lives in the southern regions of our country. The bite of a tarantula causes painful swelling in a person, but does not pose a mortal danger to him.

Among all spiders, only one poisonous spider is dangerous to humans - karakurt (Latrodectus tredecimguttatus, Fig. 304), found in the dry steppe regions of Ukraine, the Volga region, the Caucasus and Central Asia. This is a medium-sized spider (1.5 cm), black with red spots. It lives in earthen burrows and spreads cobwebs on the surface of the soil, in which orthopterous insects usually come across. Its poison is dangerous to horses and humans, but not dangerous to sheep and pigs. The female karakurt is larger than the male and, as a rule, eats it after mating, therefore the karakurt is popularly called the "black widow".

Of biological interest is the silver spider, which lives in a web bell under water. The bell spider fills with air. The spider brings air bubbles on a fluffy abdomen that is not wetted by water. When a silver spider dives deep from the surface of the water, its abdomen is covered with a layer of air and therefore it seems silver.

Large tarantulas are common in the tropics (Fig. 305).

There are a lot of spiders in all tiers of land biocenoses, and they, as predators, play a positive role in regulating the number of herbivorous insects.

The order of acariform mites is the most numerous and includes more than 15 thousand species. These are very small forms (0.2-0.3 mm). In primitive representatives of the order, the anterior part of the cephalothorax is fused and forms a department - the proterosome, consisting of an acron and four segments. The three posterior segments of the cephalothorax are free and, together with the six abdominal segments and the telson, form the second part of the body, the hysterosome. On the proterosome are pincer-shaped chelicerae, flagellate pedipalps, and two pairs of walking legs. On the hysterosome are two posterior pairs of walking legs and abdominal appendages. The rudiments of the ventral legs on the 5th-7th segments form the genital covers, between which there is a genital cone with a genital opening. Under the floor covers there are three pairs of coxal organs in the form of thin-walled bags. Primitive acariform mites have skin respiration. In evolutionarily advanced forms, the body is fused, there are tracheae, and on different segments in different families. Reproduction is spermatophoric. Development with anamorphosis. Fig. 1. 305. Tarantula spider Poecilotheria regalis (according to Millo)

The family of thyroglyphoid mites, or barn mites, causes significant damage to grain, flour and other food products. These include ticks: flour, cheese, onion and wine. In nature, thyroglyphoid mites live in soil, fungi, decaying matter, bird nests, and mammalian burrows. Thyroglyphoid mites survive unfavorable conditions in the phase of a resting nymph covered with dense chitin (hypopus). Hypopuses withstand drying, freezing. Once in favorable conditions, the hypopuses become active and give rise to a new colony of ticks.

Some groups of ticks are herbivores. This is a family of gall-forming, spider mites. Among them are many pests of cultivated plants. For example, a cereal mite is a pest of crops, a spider mite is a pest of fruit trees. Many ticks live in the soil (red heifers), in fresh waters (Fig. 306, B).

Rice. 306. Ticks (from Lang, Matveev, Berlese, Pomerantsev): A - armored mite Galumna mucronata, B - feather mite Analgopsis passermus, C - water mite Hydrarachna geographica, D - four-legged mite Enophyes, D - itch itch Sarcoptes scabiei, E - Demodex folhculorum, G - cadaveric mite Poecilochirus necrophon, H - ixodid tick Dermacentor pictus

The detachment is characterized by the formation of a complex shell. In some forms, the anterior part of the cephalothorax, corresponding to the acron and three segments, is separated from the rest of the body by a suture. But in many species, all parts of the body are fused into a solid shell. Embryonic development of ixodid ticks shows that initially the cephalothorax is formed from the acron and six segments with six pairs of limbs. The seventh segment of the cephalothorax forms a transition zone on the border with the abdomen. The abdomen is formed from merged six large segments and 2-3 rudimentary ones.

Ixodid ticks have a solid flat body. The oral apparatus forms a "head" (gnathema) and consists of cutting chelicerae, to which jointed pedipalps adjoin on the sides, forming something similar to a case. The composition of the oral apparatus also includes a hypostome - an outgrowth of the pharynx with chitinous teeth. The tick bites through the skin with chelicerae and inserts a hypostome into the wound, which is anchored with teeth. A sucking tick is therefore very difficult to remove from the skin. If you tear it off by force, then its head remains in the skin, and this can cause inflammation. Therefore, it is recommended to lubricate the sucking tick with kerosene or oil, and it will disappear by itself. This is explained by the fact that, having lubricated the tick with oil, we clog its respiratory openings and the tick weakens without breathing, relaxes the muscles and falls off.

Ixodid ticks live in the soil and climb plants. In the process of development, most ixodid ticks change hosts. So, nymphs I hatched from eggs attack small rodents, lizards, chipmunks. After drinking blood, they fall off. After another molt, they attack other prey of the same species. Adult ticks usually feed on the blood of large mammals (ungulates, dogs) and humans. Males are usually half the size of females. Females can only lay eggs by sucking blood. Ticks can starve for a long time. They attack a person from trees and from the surface of the soil. In the eastern regions of the taiga zone of our country, the taiga tick (Ixodes persulcatus) is most common. In the European part of the country, the dog tick (Ixodes ricinus) is the most common. About 50 species of ixodid ticks are known in our country. They carry pathogens of dangerous diseases: encephalitis, tularemia, piroplasmosis, typhoid fever.

the disease is carried by carriers - blood-sucking ticks from animals - carriers of the infection (reservoir) to other healthy animals and humans. A person who enters the focal zone of the spread of infection is at risk of the disease. We have a network of medical and veterinary services that detects outbreaks of dangerous diseases carried by ticks. In these areas, anti-infective vaccinations are mandatory.

Detachment Ticks-harvesters (Opiliocarina). It is noteworthy that the harvest mites have a segmented body: the last two segments of the cephalothorax are free and the abdomen of eight segments. They have four pairs of stigmas on abdominal segments 1-4. The chelicerae are claw-shaped.

Spiders ... What do we know about spiders, for many they cause fear, for many spiders cause a feeling of disgust. On our site you will get acquainted with some types of spiders. We will tell you about what varieties of spiders are, what makes them remarkable. In addition, we will dispel some of the myths that are quite strongly associated with spiders in our minds. Also, we will give you some helpful tips on how to get rid of spiders in your garden or home.

Spiders were the first among the earliest animals to live on earth. Despite the fact that the age of the 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 about four hundred million years ago. The ancestors of modern spiders were an arachnid insect, rather thick, large in size. For a fairly long period of time, this arachnid insect lived in the water. The first ancestors, which were already similar in body structure, and in other ways, to modern spiders were Attercopus fimbriungus (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 (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-shaped abdomen, belonged to the Mesothelae variety (Mesoselai). The Mesothelae group (Mesoselai) differed in that the place from which they unwound the web was in the middle of their abdomen, and not at the end of the abdomen, like their modern "relatives". It is likely that this kind of distant ancestors of spiders lived on earth, they were predators, lived in giant thickets, fern forests. These spiders lived around the middle of the Paleozoic. Apparently the Mesothelae were predators and preyed on other primitive insects such as cockroaches, roofers and centipedes. The web may well have been used simply as a protective covering for the eggs, later it is possible that the web was also used to create simple nets arranged on the ground, as well as to create a so-called hatch or loophole. Thanks to the development of evolution, including the evolution of plants, the life of spiders began to change. Spiders with a weaving device at the end of the abdomen, and these spiders were called Opisthothelae (Opissosalai) appeared more than two hundred and fifty million years ago. These spiders could already weave more complex networks, which are real labyrinths. Thus, smaller insects fell into such complicated nets directly on the ground, and nets could also be found in the foliage. With the onset of the Jurassic period (approximately one hundred ninety-one - one hundred thirty-six million years ago), during this historical period, dinosaurs already walked on our planet, air networks that were skillfully woven by spiders were already designed to trap and, accordingly, to catch, then an incredible number of insects, which were simply teeming with foliage. Approximately in the same way, with an increase in the total number of spiders on the planet, the spiders themselves became quite easy prey, thereby, the spiders were forced to adapt to the new habitat. To date, there is a sufficient amount of mined fossils, the age of which is determined as the Tertiary period. According to the analysis of fossil data, spiders can be seen as if they were trapped in the resin of trees. So, according to these fossils, the species diversity of spiders that we can observe now is quite consistent with the species diversity of these insects, which existed about thirty million years ago.

Most spiders are small, featureless arthropods that are harmless to humans. Their beneficial role in maintaining insect populations far outweighs the danger from the few spiders that occasionally bite humans. Only a few varieties of spiders are venomous; spiders and insects are waging a fairly serious fight, the preponderance of which is more often on the side of predators.

Tarantulas, jumping spiders, and some other species scare people, the latter mistakenly believe that they are a serious danger. Although these spiders are large, hairy, and unattractive in appearance, their sting is generally less dangerous than a bee sting. True, if you are allergic to spider venom, any spider bite will cause you a serious reaction. Many people are afraid of spiders, however, knowing how to distinguish harmless animals from truly dangerous ones, how to prevent them from entering the house, and how to protect yourself from those who can really 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 take a swing at small birds and animals.

Are recluse spiders the most dangerous?

While only a few of the hermits are actually venomous to humans, it is best to view the entire species as potentially dangerous.

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

poisonous spiders

In fact, poisonous spiders are not as big a threat as is commonly believed. The existing antidote for the bites of various types of spiders is very effective today, and deaths from a bite 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 must be urgently treated and carried out for long care procedures. All spiders use venom to kill their victims after they are caught in webs or captured by the spiders through other means. Poisonous spiders, on the other hand, have a more serious poison, aimed at immobilizing and killing large victims, and used by them not only for food, but also for self-defense. The likelihood of death or serious injury from a bite is very small - however, in any case, it is better to consult a doctor to avoid serious consequences.

tarantula spiders

Tarantulas have long taken their place as pets with extreme breeders. In this they are helped by an attractive appearance, variegated coloration, 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 quite long-lived pets, the average life expectancy is estimated at a couple of decades (representatives of the weaker sex). Tarantulas are tropical inhabitants, who have now gained popularity in our country as pets. As the name implies, tarantulas, at least some of their varieties, feed not just on insects, but also on birds. Of course, tarantulas, like other spiders, believe 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 until the animal is entangled in the web, but attack it from an ambush.

house spiders

Several varieties of spiders are often found in the household. With rare exceptions, they are quite harmless, being in the 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 home spiders are a black widow, a hermit, and other species that are deadly, you need to get rid of such a terrible neighborhood.

What can you do about it?

To keep spiders out of the house, you can use mechanical methods - kill them with your hands, a newspaper, a broom, or suck them out with a vacuum cleaner. Domestic spiders are also afraid of chemical sprays based on boric acid, chlorpyrifos, etc. If you patch up cracks in your home, increase the sealing of your windows, or pick up trash outside your home, house spiders are unlikely to get to you. For prevention, you can also use special sprays designed for spraying on the street. If you have been bitten by a spider, and you do not know which species it belongs to, it is better to visit an infectious disease specialist.

Dream interpretation: spiders

Arachnophobia, the fear of spiders, is the most well-known phobia among Americans, and quite common among us. Many people say that these hairy eight-legged creatures disgust them. If you look into the dream book, spiders dream of many situations that await 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 getting goosebumps from its appearance. If you have ever read any of the African tales, you may have noticed that spiders are cunning, treacherous creatures often associated with deceit. This is most likely due to their type of diet. Very often, having seen a dream, we take a dream book, spiders on it (in various interpretations) are just a warning about the danger of falling into the network of deception. Another association associated with spiders comes from their ability to weave beautiful, intricate webs. The well-known myth of Arachne, which turned into a spider, also testifies to this. If in a dream you see a web, it is quite possible that this means that your creative impulses are being ignored, spiders weaving a web indicate that inspiration is right in front of you. When considering the symbolic meaning of spiders, one cannot lose sight of the cannibalistic tendencies of many females who kill partners after mating. It can be said without looking into the dream book that spiders represent the female energy within us, and if you have dreams about the murder of your partner by a spider, it means that serious changes are coming in your life. Spiders, unlike insects, do not have antennae (antennae) and jaws. The body is covered with an external skeleton (exoskeleton) and consists of two sections - the cephalothorax, formed by the merged head and chest, and the abdomen. At the anterior end of the cephalothorax 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. On the front of the head are two downward-pointing, jaw-like chelicerae, each ending in a sharp claw. Poison glands located in these limbs open on it. 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 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 silk spinning. Breathing holes in the abdomen lead to the so-called book lungs (named for their layered structure) or plug system (trachea) for air.

The digestive system of spiders is adapted exclusively to the digestion of liquid food, because insects capture their prey and then suck the liquid out of them. Spiders have a fairly complex brain, larger or smaller in certain parts, depending on whether the animal locates prey mainly through contact or sight. With a bite, spiders paralyze prey: this is how their poison acts on the victim's nervous system. They can only eat liquid food, since the mouth opening of spiders (in the form of a tube) is very narrow. Therefore, spiders inject a special substance inside the prey, which acts like digestive juice, corroding tissues. Then they suck out the victim, leaving only an empty skin. Such digestion is called extraintestinal. All spiders are carnivorous insects by nature, and most of them live on their prey. They can survive for long periods without food. Some spiders have been kept alive for over two years without food. Spiders hunt 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 smaller than themselves and will run away from prey larger than themselves. Those that have well developed jaws (chelicerae) tear open their prey and drink the digestive juices from it. Those in which the 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 is stretched when food is absorbed, but when the maximum amount of liquid is reached, further stretching 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. Thus, the old spider must shed. The old cuticle splits and makes room for a softer cuticle that strengthens over time. Nymphs molt frequently, every few days during which their size increases, this does not happen with mature spiders. The interval between molts increases with the age of the spider. The smaller species shed about five times less than the larger spiders. Sometimes shedding doesn't go according to plan, legs get stuck, etc. Then the spider dies, or it may break its legs to set them free, they are very susceptible at this stage.