What is the basis of the complex behavior of spiders to build. Class arachnids. Practical application of the orb weaver's web
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, however, Linnaeus's point of view prevailed, but the International Congress of 1948 restored the priority of Clarke'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, the convoluted vas deferens are connected near the genital opening, which in the male has the appearance of 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 links. 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 that 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. The 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. If 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 keep within, 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 turns out to be torn in many places, also losing in 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-producing 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 the white secretions of 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: cloudy, 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, butterflies often succeed in escaping the web with strong flapping, 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 behavior of the male are aimed at overcoming the predatory instincts of the female: the male behavior differs sharply from the usual 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:
- Hilliard P. (2001) Spiders. Moscow: Astrel
- Sterry P. (1997) Spiders. Moscow: Belfast
- Kozlov M., Dolnik V. (2000) Crustaceans and arachnids. Moscow: MGU Publishing House
- Collection "Tree of knowledge"(2001-2007), volume "Animals and plants". Moscow: Marshall Cavendish
- Encyclopedia Around the World. http://www.krugosvet.ru/
- Encyclopedia Wikipedia. http://www.wikipedia.com/
- Veterinary portal "Avicenna". http://www.vivavet.ru/
Recently, scientists from Simon Fraser University in Canada described another example of a surprisingly complex behavior of spiders that does not fit in with the image of "primitive" tiny animals. It turned out that male black widows deliberately destroy the web of females in order to reduce the number of potential rivals during the mating season. Like not-too-honest businessmen ripping off competitors' ads, they wrap the web of females in special cocoons so that the pheromones it contains cannot spread through the air. We decided to look at other similar examples of complex behavior that show that spiders are not at all as simple as people think they are.
Western black widow males Latrodectus hesperus, in the course of courting a female, bundles are made from flaps of her web, which are then braided with their own web. The authors of an article published in animal behavior, suggested that this should reduce the amount of female pheromones that are released into the air from their webs and can attract rivals. To test this assumption, the scientists took four different types of webs woven by females in cages in the lab: partly coiled by males, partly cut with scissors, webs with artificially added pieces of male webs, and intact webs. The females were removed from all the webs, and then the cells with the webs were taken to the coast of Vancouver Island, where black widows live, to find out how many males various specimens will attract.
After six hours, the intact webs attracted more than 10 male black widows. Webs partially rolled up by other males turned out to be three times less attractive. Interestingly, however, the nets damaged by scissors and nets with artificially added male cobwebs attracted the same number of males as intact nets. That is, neither the cutting out of pieces nor the addition of the male's web in itself affected the attractiveness of the web. As scientists conclude, in order for the web to become less attractive to rivals, both manipulations are needed: targeted cutting of sections of the web marked with female pheromones and wrapping these sections with the web of males, which serves as a barrier to the spread of female pheromones. The authors also suggest that some compounds contained in the web of males can change the signals emitted by female pheromones.
Another example of the cunning of spiders is the behavior of males of another species of black widows, Lactrodectus hasselti. The females of these Australian spiders, which are markedly larger than the males, require at least 100 minutes of grooming before mating. If the male is lazy, the female will most likely kill him (and eat him, of course). After reaching the threshold of 100 minutes, the probability of killing is greatly reduced. However, this does not give any guarantees: even after a 100-minute courtship, a successful male in two out of three cases will be killed immediately after mating.
Spiders know how to deceive not only their women, but also predators. Yes, orb-weaving spiders Cyclosa ginnaga they disguise themselves as bird droppings, weaving a dense white “blot” in the center of their web, on which the silver-brown spider itself sits. To the human eye, this blob with a spider sitting on it looks exactly like bird droppings. Taiwanese scientists decided to make sure that this illusion also works on those for whom it is, in fact, intended - predatory wasps that prey on orb-weaving spiders. To do this, they compared the spectral reflectances of the body of a spider, "blots" from the web and real bird droppings. It turned out that all these coefficients are below the color recognition threshold for predatory wasps - that is, the wasps really do not see the difference between a camouflaged spider and bird droppings. To test this result experimentally, the authors painted the “blobs” on which the spiders sat black. This significantly increased the number of wasp attacks on spiders - spiders sitting on an intact web were still ignored by the wasps.
Orb-weaving spiders are also known for making “stuffed animals” of themselves from pieces of leaves, dry insects and other debris - real self-portraits with a body, legs and everything else that a spider is supposed to have. These stuffed spiders are placed on the web to distract predators, while they themselves hide nearby. Like fake bird droppings, stuffed animals have the same spectral characteristics as the body of the spider itself.
The Amazonian orb-weaving spiders went even further. They learned how to create not just stuffed animals, but real puppets. Having made a fake spider out of garbage, they make it move by pulling the strings of the web. As a result, the stuffed animal not only looks like a spider, but also moves like a spider - and the owner of the puppet (which, by the way, is several times smaller than his self-portrait) hides behind it at this time.
All these examples are, of course, wonderful, but they do not say anything about the "mind" of spiders and their ability to learn. Can spiders "think" - that is, find non-standard ways out of non-standard situations and change their behavior depending on the context? Or is their behavior based only on patterned behavioral responses - as is commonly expected from "lower" animals with small brains? It seems that spiders are still smarter than is commonly believed.
One of the experiments showing that spiders are capable of learning - that is, adaptive behavior change as a result of experience - was carried out by a Japanese researcher on orb weaving spiders. Cyclosa octotuberculata. These spiders weave a "classic" circular web, consisting of adhesive spiral and non-adhesive radial filaments. When the prey hits the sticky spiral filaments, its vibrations are transmitted along the radial filaments to the spider sitting in the center of the web. Vibrations are transmitted the better, the stronger the radial threads are pulled - therefore, the spiders, in anticipation of the victim, alternately pull the radial threads with their paws, scanning different sectors of the web.
In the experiment, the spiders were brought to the laboratory, where they were recreated in their natural habitat, and given time to weave a web. After that, the animals were divided into two groups, each member of which was given one fly per day. However, in one group, the fly was always placed in the upper and lower sections of the web (the "vertical" group), and in the other, in the side sections (the "horizontal" group).
Another experiment proving that the behavior of spiders is determined not only by template instinctive programs is shown in the famous film by Felix Sobolev " Do animals think(You should definitely watch it in its entirety.) In an experiment conducted in a laboratory (but, unfortunately, not published in a peer-reviewed journal), a thousand threads were lowered onto a thousand spider webs, partially destroying the webs. 800 spiders simply left the destroyed webs, but the rest of the spiders found a way out. 194 spiders gnawed the web around the thread - so that it hung freely, without touching the nets. Another 6 spiders wound the strings and firmly glued them to the ceiling above the cobweb. Can this be explained by instinct? With difficulty, because the instinct should be the same for all spiders - and only some of them "thought of" something.
As befits intelligent creatures, spiders are able to learn from other people's mistakes (and successes). This was shown by an experiment conducted by American scientists on male wolf spiders. Spiders brought from the forest to the laboratory were shown several videos in which another male performed a courtship ritual - he danced, stamping his foot. Looking at him, the audience also began a ritual dance of courtship - despite the fact that the female was not on the video. That is, the spiders "assumed" the presence of the female, looking at the dancing male. By the way, the video, in which the spider just walked through the forest, and did not dance, did not cause such a reaction.
However, this is not what is curious here, but the fact that the male spectators diligently copied the dance of the male actor. Comparing the characteristics of the dance - the speed and number of kicks - between the actors and the audience, the scientists found their strict correlation. Moreover, the audience tried to outdo the spider in the video, i.e. stomp their feet faster and better.
As the authors note, such copying of someone else's behavior was previously known only in more "intelligent" vertebrates (for example, in birds and frogs). And no wonder, because copying requires a great plasticity of behavior, which is generally uncharacteristic for invertebrates. It is curious, by the way, that the earlier experiment of the authors, which used "naive" spiders grown in the laboratory and had never seen courtship rituals before, did not give similar results. This further indicates that the behavior of spiders can change with experience, and not just determined by template behavioral programs.
An example of an even more complex type of learning is reversal learning, or reshaping a skill. In other words, retraining. Its essence is that the animal first learns to associate the conditioned stimulus A (but not B) with the unconditioned stimulus C. After some time, the stimuli are reversed: now not A, but B is associated with stimulus C. The time it takes for the animal to relearn , is used by scientists to assess the plasticity of behavior - that is, the ability to quickly respond to changing conditions.
It turned out that spiders are capable of this type of learning. This was shown by German researchers using the example of Marpissa muscosa jumping spiders. In plastic boxes they placed two LEGO bricks - yellow and blue. Behind one of them was hidden a reward - a drop of sweet water. The spiders released at the opposite end of the box had to learn to associate either the color of the brick (yellow or blue) or its location (left or right) with the reward. After the spiders were successfully trained, the researchers proceeded with a retraining test: swapping either the color, or the location, or both at once.
The spiders were able to relearn, and surprisingly quickly: it only took one attempt for many to learn to associate the reward with the new stimulus. Interestingly, the subjects differed in learning abilities - for example, with an increase in the frequency of training, some spiders began to give correct answers more often, while others, on the contrary, began to make mistakes more often. The spiders also differed in the type of key stimulus they preferred to associate with the reward: some found it easier to “relearn” the color, and others the location of the brick (although most still preferred the color).
The jumping spiders described in the last example are generally remarkable in many ways. A well-developed internal hydraulic system allows them to lengthen their limbs by changing the pressure of the hemolymph in them (an analogue of blood in arthropods). Thanks to this, jumping spiders are able (to the horror of arachnophobes) to jump a distance several times their body length. They also, unlike other spiders, easily crawl on glass - thanks to tiny sticky hairs on each foot.
In addition to all this, horses also have unique vision: they distinguish colors better than all other spiders, and in terms of visual acuity they surpass not only all arthropods, but in some aspects even vertebrates, including individual mammals. The hunting behavior of jumping spiders is also very complex and interesting. As a rule, they hunt in the manner of a cat: they hide in anticipation of prey and attack when it is close enough. However, unlike many other invertebrates with their stereotypical behavior, jumping spiders change their hunting technique depending on the type of prey: they attack large prey only from behind, and small ones - as they have to, they chase a fast-moving prey themselves, and wait for a slow one in ambush .
Perhaps the most surprising in this respect are the Australian jumping spiders. During the hunt, they move along the branches of a tree until they notice the victim - the orb-web spider, which is capable of self-defense and can be quite dangerous. Noticing the prey, the jumping spider, instead of heading straight for it, stops, crawls to the side and, having studied the surroundings, finds a suitable point above the victim's web. Then the spider gets to the chosen point (and often for this he has to climb another tree) - and from there, releasing a cobweb, jumps onto the victim and attacks it from the air.
This behavior requires a complex interaction between different brain systems responsible for image recognition, image categorization, and action planning. Planning, in turn, requires a large amount of working memory and, as scientists suggest, involves compiling an “image” of the chosen route long before the start of movement along this route. The ability to make such images has so far been shown only for very few animals - for example, for primates and corvids.
Such complex behavior is surprising for a tiny creature with a brain diameter of less than one millimeter. Therefore, neuroscientists have long been interested in the jumping spider, dreaming of understanding how a small handful of neurons can provide such complex behavioral responses. However, until recently, scientists could not get to the brain of a spider to record the activity of neurons. The reason for this is all in the same hydrostatic pressure of the hemolymph: any attempts to open the spider's head led to a rapid loss of fluid and death.
Recently, however, American scientists finally managed to get to the brain of a horse spider. Having made a tiny hole (about 100 microns), they inserted the thinnest tungsten wire into it, with which they were able to analyze the electrophysiological activity of neurons.
This is great news for neuroscience, because the jumping spider brain has some very research-friendly properties. Firstly, it allows you to separately study different types of visual signals by closing the spider's eyes in turn, of which it has as many as eight (and most importantly, these eyes have different functions: some scan stationary objects, while others react to movement). Secondly, the brain of a jumping spider is small and (finally) easily accessible. And third, this brain controls behavior that is surprisingly complex for its size. Research in this area is just beginning today, and in the future, the jumping spider is sure to tell us a lot about how the brain works - including our own.
Sofia Dolotovskaya
Subtype Cheliceraceae (Chelicerata)
The body of the chelicerates consists of a cephalothorax, from which six pairs of appendages extend: chelicerae for fixing food pedipalps , serving for touch, chewing food, and also as a copulatory organ and four pairs of walking legs. Representatives of the subtype are known from the Cambrian (terrestrial forms - from the Devonian) and are combined into four classes: horseshoe crabs , scorpions , sea spiders and arachnids .
Class Arachnida (Agachnida)
Arachnids are the most prosperous group of chelicerae animals, numbering 60,000 species. It includes spiders, scorpions And false scorpions, saltpugi, haymakers, ticks and other animals. The science that studies arachnids is called arachnology (from Greek. Arachne- Spider; this was the name, according to one of the myths, of the weaver, whom the angry Athena turned into a spider).
Representatives of arachnids are eight-legged land arthropods, in which the body is divided into cephalothorax And abdomen connected by a thin constriction or merged. Arachnids do not have antennae. Six pairs of limbs are located on the cephalothorax - chelicerae, leg tentacles and four pairs of walking legs. There are no legs on the abdomen. Their respiratory organs are lungs And trachea . The eyes of arachnids are simple. Arachnids are dioecious animals.
The body length of various representatives of this class is from 0.1 mm to 17 cm. They are widely distributed around the globe. Most of them are land animals. Among ticks and spiders there are secondary water forms.
The external structure and lifestyle of spiders
cross spiders (so named for the cross-shaped pattern on the dorsal side of the body) can be found in the forest, garden, park, on the window frames of suburban and village houses. Most of the time, the spider sits in the center of its trapping web of adhesive thread - cobwebs .
The body of the spider consists of two sections: a small elongated cephalothorax and a larger spherical abdomen. Abdomen separated from cephalothorax constriction . At the anterior end of the cephalothorax, there are four pairs of eyes above, and below, hook-shaped hard jaws - chelicerae . With them, the spider grabs its prey. There is a canal inside the chelicerae. Through it, poison from the poisonous glands located at the base of the chelicerae enters the body of the victim. Next to the chelicerae are short organs of touch covered with sensitive hairs - leg tentacles (pedipalps) . four couples walking legs located on the sides of the cephalothorax. The body is covered with light, durable and quite elastic chitinous cuticle . Like crayfish, spiders periodically molt, dropping their chitinous cover. At this time they are growing.
At the lower end of the abdomen are three pairs arachnoid warts that produce webs are modified abdominal legs.
Building a trapping network
The most beautiful, wheel-shaped nets (trapping nets) are built by female orb-weaving spiders from the cross family. First, the spider climbs to a high place, usually near an open space (path), and secretes a very light thread, which is picked up by the breeze and, accidentally hitting a neighboring 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 threads are laid, making up a closed frame, inside which the network itself will be located. Then the thread-radii are pulled, connecting in the center. After that, starting from the center, the spider moves to the periphery in a spiral. The spiral thread of the web is covered with droplets of a sticky secret. A signal thread stretches from the web to the spider. The female is waiting for the signal thread to fluctuate. Then the spider rushes to the prey, bites, injects poison with its upper jaws and leaves, waiting.
The internal structure of the spider-cross
In a spider, like in other crustaceans, the body cavity is of a mixed nature - in the course of development it arises when the primary and secondary body cavities are connected.
Digestive system. The cross spider cannot eat solid food. Having caught prey, such as some kind of insect, with the help of a web, he kills him poison and let into his body digestive juices . After some time, the contents of the caught insect liquefies, and the spider sucks it out. Only an empty chitinous shell remains from the victim. This type of digestion is called extraintestinal .
The digestive system of a spider consists of a mouth, pharynx, esophagus, stomach, and intestines. In the midgut, long blind outgrowths increase its volume and absorption surface. Undigested residues are brought out through the anus.
Respiratory system. The respiratory organs of a spider are the lungs and trachea. Lungs or lung bags are located below the abdomen, in front of it. These lungs evolved from the gills of distant ancestors of aquatic spiders. The cross spider has two pairs of non-branching trachea - long tubes with special spiral chitinous thickenings inside. They are located in the back of the abdomen.
Circulatory system in spiders open
. The heart looks like a long tube located on the dorsal side of the abdomen. Blood vessels branch off from the heart. Like crustaceans, spiders have hemolymph circulating in their bodies.
excretory system represented by two long tubes - malpighian vessels . With one end, the Malpighian vessels blindly end in the body of the spider, with the other they open into the posterior intestine. Metabolic products are removed through the walls of the Malpighian vessels, which are then brought out. Water is absorbed in the intestines. In this way, spiders conserve water, so they can live in dry places.
Nervous system The spider consists of the cephalothoracic node and numerous nerves extending from it.
Reproduction. Fertilization in spiders is internal. Mating of crosses occurs at the end of summer. The male carries the spermatozoa into the female genital opening with the help of special outgrowths located on the front legs. Spiders have poor eyesight, with the help of 8 simple eyes they see poorly. The male needs to be very careful not to be mistaken for prey by the female. Immediately after mating, the spider is hastily removed, as the behavior of the female can change dramatically, and slow males are often killed and eaten.
The female lays several hundred eggs by autumn. cocoon from the web. Hiding it under the bark, under the stones. Dies by winter. In the spring, spiders crawl out of the cocoon, climb up the branches and, with gusts of wind, fly away on the web and settle. The complex behavior of a spider: the construction of trapping nets, flight devices, dwellings is instincts , i.e. norms of behavior inherent in each species, which are inherited.
Arachnids are mostly terrestrial arthropods. They breathe with lungs or windpipes. Their body is divided into the cephalothorax and abdomen, or it is fused. Outwardly, arachnids can be distinguished from other arthropods by the following features: they have no antennae, two pairs of mouth organs, and four pairs of walking legs. The complex behavior of spiders (building trapping nets, cocoons) is based on instincts.
CLASS ARCHINA
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 inhabited a wide 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.
Scorpions are 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.
The risk of writing an article about spiders and their terrifying relatives is that while studying information about these creatures, deep down you will constantly want to throw a slipper at the monitor, and not read, let alone watch photos and videos. After all, all these terrible and disgusting arachnids want to do is eat your face. Yes, yes, it is your face, dear reader. But if you can shake off the feeling of fear and disgust, you will know that these small insects actually have remarkable intelligence and sociability. But among them, of course, there are several that are the definition of the word "horror", so you can not put your slipper far away.
10. Males eating females
Many of us have heard that female spiders sometimes eat males. This makes more sense - the male loses any chance of breeding in the future, but the female, who received a good meal, is more likely to carry eggs before the young are born. The spider species Micaria sociabilis turns this concept on its head, as 20 percent of matings end with the male eating the female. However, this species of spider is not the only one showing this behavior, but there is no obvious explanation for it.
Researchers in the Czech Republic hoped to find an answer by noting which females end up being eaten. Micaria sociabilis produce two generations of young each year, one in spring and one in summer. When males were with females from both groups, they were more likely to eat older females and release their younger mates. Using older females for food to increase your chances of mating with younger females is a strategy that seems to work, as younger females are more likely to raise offspring.
9. Matriphagy
Given the black widow's bad reputation, any spider with the word "black" in its name immediately makes us wary. The black weaver of the species Amaurobius ferox is no exception - it has a very unflattering way of being born. When little spiders hatch from the eggs of this species, the mother encourages them to eat her alive. When nothing is left of her, they climb onto her web and hunt in groups of 20 individuals, killing prey 20 times their size. Young spiders also ward off predators by contracting their bodies at the same time, giving the impression of a pulsating web.
Another spider that devours its mother is the Stegodyphus lineatus spider. Newborn spiders of this species live for some time, feeding on the liquid that their mother regurgitates for them. They end up liquefying her organs and drinking them - and they do it with her permission.
8. Family life
Photo: Acrocynus
Common names for arachnids are often depressingly incorrect. Phrynes, or as they are also known as bugle-legged spiders, are not spiders. They belong to a completely different order of arachnids. These eight-legged creatures resemble some kind of spider-scorpion hybrid, but with whips. If this image does not make you want to embrace these creatures, let me introduce you to the inhabitant of the state of Florida - the species Phrynus marginemaculatus, as well as the inhabitant of Tanzania - Damon diadema.
Researchers at Cornell University have found that these types of phrynes like to live together in family groups. The mother and her grown cubs got together again after they were separated by scientists. The groups act aggressively towards strangers and spend their time constantly petting and grooming each other. Scientists think cohabitation may well help these arachnids ward off predators and allow mothers to protect their broods.
7. Fatherly care
And how do spider fathers help their children? Of course, there are those who offer themselves as a dinner to the mother of their future children. But this is a choice for lazy people. Fathers of tropical harvestmen are actively involved in raising offspring: they take on the role of nest guards as soon as the female lays eggs. Without fathers to protect them, the eggs would simply not hatch. The fathers drive the ants away, repair the nest, and clean up the mold—sometimes within months.
This method is suitable for males for several reasons. First, in this way, they impress the females and win their favor. The male can look after the clutches of 15 females at the same time. The scientists also found that males who take care of their offspring have a much higher chance of survival than careless dads. Perhaps this is because their stationary position keeps them from encountering animals that love to prey on spiders, in addition, females take care to leave slime around their nests and, accordingly, the male, which helps drive predators away from the nest.
6. Distribution of tasks depending on the characteristics of the character
Speaking of the genus of spiders known as Stegodyphus, one cannot ignore a special kind of arachnid known as Stegodyphus sarasinorum. Although they also liquefy their mother's innards and drink them, they also have an interesting characteristic. They live in colonies, in which tasks are distributed in accordance with the nature of this or that individual. Scientists tested the aggression and courage of spiders by touching them with sticks or with the help of wind blows. They marked the spiders with multicolored markings to track individual spiders. The scientists then allowed the spiders to organize their colony.
After that, the team decided to run a test to determine which of the spiders would come out to examine which floundering insects were stuck in their webs. Spiders respond to the vibrations that pass through the web when insects twitch in it. Shaking the web with your hand would create exorbitant vibrations, so scientists used an electrical device that was specifically tuned to create certain vibrations. The little pink device is called Minivibe Bubbles. What these devices were originally intended for - guess for yourself.
The scientists found that those that ran after prey were those that had previously shown a more aggressive nature. This is quite understandable, and such a division of duties can bring to the colony the same benefit that the division of labor brings to our society.
5. Courtship in the most appropriate way
Male wolf spiders put a lot of effort into making a good first impression on ladies. The key to success with them, as with humans, is effective communication. Several independent studies have shown how male wolf spiders alter the way they signal potential mates for maximum effect.
Researchers at the University of Cincinnati placed male wolf spiders on rocks, on the ground, on wood, and on leaves, and found that their signaling vibrations were most effective when they were standing on leaves. During a second set of tests, they gave the spiders a choice and found that wolf spiders spent more time signaling on leaves than on other materials. In addition, when males were on less than ideal surfaces, they relied less on vibrations and paid more attention to visual effects such as raising their legs.
However, changing the method of communication is not the only trick that wolf spiders have hidden up their eight sleeves. Scientists from Ohio State University noticed that male wolf spiders in the wild tried to imitate their competitors in order to be more successful with the ladies. To test this theory, the scientists captured several wild male wolf spiders and showed them a video of another male wolf spider doing a mating dance. Caught males immediately copied it. This ability to copy and act on what is seen is a complex behavior that is quite rare among small invertebrates.
4. Interspecific societies
Social spiders, that is, those that live in colonies, are quite rare. However, the scientists found a colony of two spider species living together. Both spiders belonged to the genus Chikunia, which makes them as close relatives as wolves are related to coyotes or modern humans to Homo erectus. Lena Grinsted, a Danish researcher, discovered the unusual settlement when she was conducting experiments to see if females would reliably protect the broods of other females of their own species.
It soon became clear that there were two kinds of spiders in the colony she was studying. The discovery was made after conducting genetic analysis and studying the difference in the genitalia of different species. The benefits of cohabitation have not been elucidated, as neither species has something that the other species needs. They do not hunt together and cannot interbreed. The only possible advantage is the mutual care of the offspring, since the females of both species are happy to look after the broods, regardless of their species.
3. Selective aggression
Most of the arachnids on this list that live in colonies usually hunt in groups. The orb-web spider living in a colony does not fit this pattern of behavior. These spiders live in colonies but hunt alone. During the daytime, hundreds of spiders relax in a central web suspended between trees and bushes with a huge amount of threads. At night, when hunting time comes, spiders build their own webs on long threads in order to catch insects.
When one spider has chosen a place and built his web, he does not intend to tolerate the presence of other spiders trying to take advantage of the fruit of his efforts. If another member of the colony approaches, the web builder jumps on it to scare away the intruder. Usually such border violators understand what's going on and go to another site to build their web - but everything changes if all the good places are already taken.
If there is no space around to weave their own webs, webless orbweb spiders will ignore the web builder's irritable jumps and remain on its web. The web builder will not attack, and an uninvited guest can usually catch his own dinner, taking advantage of the efforts of his fellow. However, they never fight because it's not worth it - threatening jumps are more of a friendly "have you looked elsewhere" question?
2. Gifts and tricks 
When a male Pisaurid spider spots a female he would like to mate with, he tries to impress her with a gift. Usually the gift is a dead insect, which is proof that he knows how to get food (and, accordingly, can pass on good genes). Males even wrap their gifts, although they lose a lot by not learning how to make a bow out of their silky web. On average, non-gifting males mate 90 percent less than their generous counterparts.
Sometimes it is very difficult to get a tasty fly, or it can be so tasty that the male himself wants to eat it before he has a chance to give it to his lover. In this case, it will simply wrap an empty insect corpse, or any piece of trash of a similar size that is lying around. This works quite often, and males who give fake gifts mate many more times than those who do not give them anything. However, females quickly figure out the deception and give unscrupulous suitors less time to leave their sperm in them than those males who brought edible gifts.
1The blood-drinking spider that loves dirty socks 
Evarcha culicivora, also known as the "vampire spider", is a rather unusual creature. It gets its name from the fact that it glistens in the sun and... oh no, apparently it gets its name from the fact that it enjoys drinking human blood. Although it certainly sounds terrible, one of the most interesting features of the spider is that it does not receive its dinner directly - it eats mosquitoes that have just drunk human blood. The vampire spider is the only animal known to choose its prey based on what it has just eaten.
When it smells blood, the spider goes berserk, killing up to 20 mosquitoes. This makes the vampire spider potentially useful, as the mosquito species it kills, Anopheles gambiae, is a malaria vector. By controlling the numbers of these mosquitoes, the spider saves lives.
Due to the fact that his dinner is usually hung around people, so does the spider. He is attracted to the smell of human settlements, including the smell of dirty socks. Scientists did an experiment in which they put a vampire spider in a box. In one case there was a clean sock in the box, in the second it was dirty. The spiders lingered longer at the dirty socks. Scientists hope that this knowledge will help them attract populations of this beneficial spider to areas where the population of harmful mosquitoes needs to be reduced.