Class Arachnids
Arachnids are mainly land arthropods. Only a few of them have moved on to living in water. Arachnids include various spiders, ticks, scorpions. Animals of this class differ from other arthropods in that their body consists of a solid chest and usually an undivided abdomen. They have no antennae and compound eyes; they move on four pairs of walking legs. Currently known
more than 35 thousand species of arachnids.
Spiders habitat, features of their structure and life.
In the second half of summer, in forests and gardens, under various canopies, you can often see webs of cross spiders and the hosts of the web. Cross spiders can be recognized by a smooth spherical abdomen, on the dorsal side of which a pattern in the form of a cross is visible. In living quarters, sheds, a house spider is common. His net has a vidhamak. A silver spider lives in ponds, backwaters of rivers. In the water, he constructs a dwelling from a cobweb in the form of a small bell, filling it with air bubbles.
Spiders have a small cephalothorax and a large non-segmented abdomen. On the cephalothorax there are eight simple eyes, claw-like jaws and leg-tentacles (organs of touch), four pairs of walking legs. Spider legs end in comb claws. With their help, they weave trapping nets made of cobwebs, which are produced in the spider glands located at the posterior end of the abdomen. The ability to secrete cobwebs has provided spiders with a high survival rate in nature: thanks to nets made from cobwebs, they catch prey, make cocoons that protect eggs from adverse effects, and run fast.
Predatory spiders. They feed mainly on insects and other small arthropods. The spider injects a poisonous liquid into the caught prey, which kills the victim and acts as a digestive juice. After about an hour, the spider sucks out the entire contents of the prey with the help of the sucking stomach.
Spiders breathe atmospheric air. They have pulmonary sacs and trachea. The circulatory, nervous and other organ systems in spiders are about the same as in other arthropods.
Other arachnids. Small arachnids - ticks live in the soil, in the organs of plants, on the body of animals and humans. Their bodies are usually fused. They breathe through the trachea or lungs.
In hot regions (in Central Asia, in the Caucasus, in the Crimea), rather large arachnids live - scorpions. Unlike spiders, they have a long articulated abdomen. Scorpions catch and hold their prey with their legs, on which pincers are developed. On the last segment of the abdomen, scorpions have a sting with ducts coming from the venom glands. With a sting, they wound prey, let poison in it, and then eat it.
The meaning of arachnids. Most arachnids destroy flies, which is of great benefit to humans. Many species of soil mites are involved in soil formation. Many species of birds feed on spiders.
There are many arachnids that cause great damage to human health and the number of game animals. Of the spiders, the karakurt living in Central Asia, the Caucasus and the Crimea is especially dangerous. Horses and camels often die from its poison. Dangerous for humans and the poison of a scorpion. The bite site becomes red and swollen, nausea and convulsions appear. Only a doctor can provide the necessary assistance to the victim.
Itch itching causes great harm. They can get into the skin of animals and humans, gnawing passages in it. From the eggs laid by the female, young mites appear, which come to the surface of the skin and gnaw through new passages. In humans, they usually settle between the fingers.
The most dangerous disease spread by blood-sucking ticks is taiga encephalitis. The carrier of its pathogens is the taiga tick. Digging into a person's skin, he brings in the blood of the causative agents of encephalitis, which then penetrate into the brain. Here they multiply and strike him.
Scorpio squad
Scorpio squad (Scorpiones) - the most ancient arachnids. About $ 600 $ species are known. Scorpions are characterized by dismemberment of the body: a fused cephalothorax, $ 6 $ segments of the peritoneal and posterior abdomen. The telson has a characteristic swelling containing a poisonous needle. Scorpions live in countries with warm climates. These are predators that hunt at night, mainly insects. Viviparity and caring for offspring are characteristic. The female carries offspring on her back for some time, throwing her back abdomen and a poisonous needle on her back. The most widespread scorpions are in Central Asia, in the Crimea, in the Caucasus, the variegated scorpion.
Squad Harp Legs, or Teliphones
Telephones (Uropygi) - these are relatively large, up to $ 7.5 $ cm arachnids, few in number, living mainly in the tropics. In Russia, in the Ussuriysk Territory, there is only one type of telephone.
Remark 1
A characteristic feature of flagellates is the presence of long sensory appendages and a special long, segmented tail filament in place of the first pair of walking legs. This thread is the sensory organ.
Telephones are nocturnal predators. These animals orientate in space, mainly due to the seismic sense and organs of touch located on the sensory limbs. Telephones have anal glands that spray out corrosive liquid when in danger.
Solpuga squad
Solpuga squad (Solifugae), or phalanges are large representatives of arachnids living in deserts and steppes. About $ 600 $ species are known.
Specific traits:
- non-fused cephalothorax;
- powerful pincer chelicerae close in a vertical plane;
- breathing through the trachea.
The phalanges of solpugs are not poisonous. They hunt at night, feeding mainly on insects. The female lays eggs in the burrow and takes care of the offspring.
False Scorpion Squad
False Scorpion Squad (Pseudoscorpiones) - small arachnids from $ 1 $ to $ 7 $ mm. They have large pincer pedipalps. Fused cephalothorax and abdomen undivided into the anterior and posterior abdomen.
False scorpions live under the bark, in the forest floor, you can find them in human dwellings. Predators feed on small insects, mites. In the houses you can find a false scorpion of the book. It appears in damp areas, which are conducive to the development of small mites and insects.
Squad Haymakers
Squad Haymakers (Opiliones) Is a common group of arachnids that resemble spiders in appearance. They differ from spiders in the absence of constrictions in the area of the cephalothorax and abdomen. Haymakers have a segmented abdominal region and pincer chelicerae.
Haymakers are found on soil surfaces, on the walls of fences and houses. In the bark of trees. Nocturnal predators feed on small insects. They actively hunt for their prey, do not emit a web.
Remark 2
A characteristic feature of haymakers is autotomy - self-mutilation when captured by other predators. In this case, the lost legs are not restored.
Spider Squad
Spider Squad (Aranei) is the most extensive order of arachnids and includes more than 27,000 species.
Spiders have characteristic morphological features:
- in the body there is a solid cephalothorax and a solid rounded abdomen, between which the constriction is located;
- chelicerae hook-shaped, contain ducts of poisonous glands;
- short pedipalps look like tentacles;
- arachnoid warts are located on the underside of the abdomen.
The widespread environmental radiation of spiders is determined by complex behaviors associated with lifelong use of spider webs.
- A dwelling is built from a web between branches, leaves or in a soil burrow.
- The cobweb envelops the egg-laying with the formation of an egg cocoon.
- Small spiders can secrete a long thread that blows them long distances in the wind.
- The web is widely used for catching prey, during the mating season.
Only bipulmonary spiders live in Russia, the most prominent representatives of which are the cross spider, house spider, silver spider, tarantula.
For humans, a spider is a danger - karakurt, which can be found in the dry steppe regions of the Caucasus, the Volga region, Central Asia.
Mites
Among the tick-like arachnids, three orders are distinguished.
Arachnids are divided into several rows, uniting about 70,000 species, common on all continents. Representatives of or Phalanges(Solifugae), False scorpions(Pseudoscorpiones).
Spiders - a group of arachnids, the characteristic features of which are the presence of venom glands and the ability to make cobwebs. This is the largest group of arachnids, which describes about 30,000 species (in Ukraine - more than 400), which have taken possession of the land from the polar regions and high mountains to the steppes and deserts. Only one species lives in fresh water - silver spider, that breathes the air that fills an underwater nest built of cobwebs.
Internal structure of the spider-spider: A - simple eyes; B - sucking stomach; V - heart; G - malpighian vessels; D - spider glands; E - sex gland; F - hole of trochea; C - trachea; AND - pulmonary sacs; AND - blind processes of the intestine; K - cephalothoracic ganglion; L - poisonous gland; M - leg tentacles (pedipalps) ; N - chelicerae
And in general, in all spiders, the relationship with the environment is carried out through spider web activity, it is based on instincts. The web plays an extremely important role in their life: they build fishing nets and cocoons from it for laying eggs, braid the victim before sucking it, lining the walls of the kidneys and lids to close the entrance to the burrow, use it to settle young people in the air, and the like. The development of the spider's glands in spiders became the reason for the progressive development of this group of animals. Spiders are carnivores that feed on a wide variety of animal foods. The only herbivorous species whose diet is 90% special excretions of acacia leaves is Bagheera Kiplinga. The venom of some spiders is dangerous to human health and life, for example, tarantula and karakurt. Tarantula distributed in the south of Ukraine and can even penetrate the territory of the forest zone, and karakurt- in the Crimea and the steppe zone. Tarantula bites cause severe pain and swelling. Karakurt bites have much more serious consequences: severe pain throughout the body, mental agitation, which is soon replaced by loss of consciousness. Jumping spiders are interesting in that they have very good object vision, which allows them to see the fly in detail at a distance of 8 cm. In addition, they can distinguish between colors. The lifespan of spiders varies, but most of them complete their life cycle within one year. The most are tarantula spiders, who can live for at least 7> 8 years. In the premises of a person lives home spider, which is distributed all over the world. This spider builds its flat, triangular fishing net with a wide funnel that goes into a tube at the corners. Among the spiders there are species that do not weave trapping nets. For instance, wolf spiders are vagrants who ambush prey, catching up with it in several jumps.
Scorpions - a group of arachnids, in which the body is dismembered into a cephalothorax and a long, segmented abdomen with a sting. This is one of the most ancient groups of arthropods.
Currently, about 700 species are described that are inhabitants of hot and warm regions of the world. In Ukraine, these animals are found in Crimea ( Crimean scorpion), Odessa and Transcarpathian regions ( carpathian scorpion). They have long
the articulated abdomen, on the last segment of which contains two poisonous glands, opens with ducts at the end of a sharp marginal sting. The bites of the scorpions that live in our area are usually not fatal for humans, but they cause severe pain, swelling of the extremities, fever, drowsiness, etc. An antitoxic serum is used as a specific remedy against bites. Bites from large tropical species (e.g. African scorpion, which is about 17 cm long) can sometimes lead to death. The prey scorpions catch and hold the tentacles ending in pincers. Scorpions are nocturnal predators. All day long scorpions hide under stones, in earthen burrows, under bark, in cracks in rocks and adobe walls of buildings, between woods and can penetrate into dwellings. They feed only on live prey, in particular insects, their larvae, spiders, etc. Most scorpions are viviparous, some lay eggs, from which young scorpions develop. The female gives birth to several dozen developed individuals, which for a certain time sit on the mother's back. Scorpions reach sexual maturity at the age of 4-5 years.
Mowing - a group of arachnids, whose body has a segmented abdomen connected to the cephalothorax by a wide base, and not by a stalk. There are more than 6300 species of them, and the territory of Ukraine - about 50.The most common species is an ordinary haymaker. The integument, as a rule, is very hard, carapace. Coloring in nocturnal forms is grayish, brown or black, in daytime forms it is variegated. Chelicerae armed with claws. The walking legs in mowers are extremely long - they can reach 16 cm. The increased flexibility allows the mowers' legs to firmly wrap around the blades of grass, helping to move in the grass. In arid areas, long legs are adaptive - they raise the body of the mowers high above the surface of the soil heated during the day. In most long-legged mowers, the legs easily come off (autotomy) and continue to contract rhythmically for a long time. Mowers are not poisonous and do not have spider glands.
They have odor glands that secrete a sharp odorous secret, through which mowers are almost not consumed by predators. These creatures are widespread almost everywhere and are found in a wide variety of biotopes - from forests and meadows to deserts. Deciduous and mixed forests are especially rich in mowers; they are also common in urban landscapes.
The importance of arachnids in nature and human life can hardly be overestimated. After all, they are an important element in the food chain, regulate the number of insect species, and some can even be deadly. The meaning of arachnids in nature and human life will be briefly outlined in our article.
Characteristic features of the structure of arachnids
But first, let's figure out by what criteria animal organisms are classified as this systematic unit.
These are representatives of the arthropod type, the body of which consists of the cephalothorax and abdomen. On the first of them there are six pairs of limbs - these are chelicera, with the help of which arachnids pierce the body of the victim. There are also legs and four pairs of walking legs. These animals are devoid of antennae. There are no limbs on the abdomen, but they can be modified into arachnoid warts or pulmonary sacs. Structural features determine the value of arachnids in nature.
What is spider web
The overwhelming majority of arachnids are able to build trapping nets from a special substance found in special warts. They emit strands that are as strong as steel wire. The spider web pattern is characteristic of each species. There are drops of sticky liquid on the spirally twisted threads. If an insect falls into it, then he has little chance of getting out. In addition to the trapping net, dwellings and cocoons are made from this substance. The value of arachnids in nature and human life is also determined by the way of feeding.
Predatory spiders
All types of spiders are predators, but their hunting methods are completely different. To get a victim, you do not have to lie in wait and pounce on it like jumping spiders. Many species use a trapping net for this. Once in it, the insect tries to escape. At the same time, the threads of the web begin to vibrate. One of them is always attached to the limb of the predator. He only has to approach the victim and kill her.
The value of arachnids in nature and human life is also due to the way of digestion. They can only eat liquid food. Through the hole that the spider makes in the victim's body with the help of a chelicera, it injects digestive enzymes inside. After a certain period of time, the spider pumps the already digested contents into its intestines with the help of its own sucking stomach.
A tarantula can also be dangerous for humans. Their venom causes severe pain throughout the body, tremors and loss of consciousness. In this state, a person needs to inject a special serum, and burn the bite site with a match to stop the spread of toxins.
The value of arachnids in nature and human life
It is worth noting that predatory spiders never attack humans in order to profit. They do it for protection. But their poison can be deadly. However, most often spiders prey on small inhabitants of reservoirs and insects. By destroying the latter, they thereby regulate their numbers. Thus, the number of blood-sucking agriculture is reduced. This, of course, determines the positive value of arachnids in nature and human life. Spider venom is a raw material for the production of sleeping pills and sedatives. To obtain them, many species of spiders are bred artificially.
Ticks: the importance of arachnids in human life
Modern taxonomy divides the class of arachnids into nine orders. The most common are spiders, ticks and scorpions. The significance of arachnids in the life of people and nature has different systematic categories of this type.
Everyone knows that walking in the forest belt in late spring and early summer can be dangerous. Indeed, it is during this period that ticks are actively multiplying and looking for food sources for themselves. Their body consists of accrete cephalothorax and abdomen, and the head is formed by legs and chelicerae. Ticks are also distinguished from other arachnids by an indirect developmental cycle. This means that a larva with three pairs of legs develops from an egg, which eventually transforms into four.
Habitat
The great importance of arachnids in nature and human life is also due to their wide distribution. These are not only forests, salt and fresh water bodies, soil, various plants, the surface, as well as the body of animals and humans - all these environments are excellent for the nutrition and life of ticks.
The negative significance of arachnids in the life of people and nature lies in the fact that many are causative agents of very dangerous diseases. Feeding on the blood of humans and animals, they can tolerate encephalitis, and dogs, relapsing fever.
Protection methods
To protect yourself from ticks, when going for a walk, you need to cover your body with tight clothing and a hat. Back home, look through all the things, remove and destroy the dangerous arachnids.
In order not to give the barn mite a chance to develop, it is necessary to monitor the hygiene in the house, periodically change bed linen, dry pillows and mattresses in the sun, and more often carry out wet cleaning of the room.
Scorpions
Scorpions are also prominent representatives of the arachnid class. Most of them live in tropical regions and in the subtropical regions. On the back of their abdomen are glands containing a poisonous substance. The ducts of the toxic glands are opened with a needle that ends in the abdomen. Scorpion venom is very dangerous for human health and sometimes life.
Benefit and harm
But, as they say, there is a silver lining. An important positive value of arachnids in nature and human life lies in their participation in soil formation processes. For example, being saprotrophs, they decompose dead organic matter. At the same time, the soil is enriched with nitrogen, which is so necessary for plants for the development of the root system. By destroying harmful insects and other arthropods, many types of ticks help to save crops of cultivated plants, prevent the spread of deadly diseases.
Thus, the importance of arachnids in nature, human life is great, both negative and positive.
1. General characteristics of the class of arachnids.
Arachnids were the first arthropods to inhabit the land and adapted to various terrestrial conditions of existence. In the course of evolution, they diverged into many different forms. This class includes scorpions, mowers, spiders, ticks, etc. The external structure of arachnids is characterized by the presence of a fused cephalopod and a dismembered or fused abdomen. The antennae and compound eyes are absent on the head (there may be several simple eyes). There are six pairs of limbs on the cephalothorax. The first two pairs (chelicerae and pedipalps) are strongly modified, they are involved in capturing, holding and killing prey. The other four pairs are walking legs. The abdominal limbs are reduced or modified into lungs and arachnoid warts. Respiratory organs - lungs, modified gill legs of ancient ancestors, trachea, or both at the same time. The excretory organs are represented by malpighian vessels. In the nervous system, the epipharyngeal ganglion (brain) is highly developed. The number of nerve nodes depends on the degree of dismemberment of the body. The digestive system is divided into three sections, but the structure of the intestines varies depending on the type of diet. The digestive system is most complex in predatory arachnids with extraintestinal digestion. The degree of development of the circulatory system depends on the structure of the respiratory organs and the size of the animal. In small forms, the circulatory system may be absent. Arachnids split-sex. In connection with the arrival on land, external fertilization is replaced by external-internal fertilization. Direct development (with the exception of mites).
2. The variety and practical importance of arachnids.
The order of spiders includes very poisonous karakurt living in the steppes and deserts, as well as tarantulas that are found in the dry steppes of southern Europe, Kazakhstan and Central Asia. Many spiders are beneficial by killing harmful insects. Many small mammals, birds, lizards, frogs, predatory insects feed on spiders. Material from the site
Arachnids include ticks, in most of which the body is not dissected into segments (the cephalothorax and abdomen grow together). These are the blood-sucking ticks - taiga and dog ticks, which often attack humans. Their oral apparatus is very much modified and serves to pierce the host's skin and feed it with blood. A stuck tick is very difficult to remove. However, the main danger lies in the fact that dog and taiga ticks are carriers of causative agents of dangerous diseases: taiga encephalitis, typhus, tularemia. In addition, among the ticks there are causative agents of human diseases such as scabies (itch itching). A large group is composed of saprophagous soil mites. Feeding on decaying residues, they contribute to an increase in soil fertility.
The development of ticks occurs with metamorphosis. A six-legged larva emerges from the egg and develops into an eight-legged nymph, followed by the adult tick stage.
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On this page material on topics:
- the practical value of arachnids for humans
- Grade 7 biology variety of arachnids. pincers
- arachnids and practical value
- abstract on arachnids with literature
- arachnid systems summary
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