Class Arachnids today has more than 35 thousand different species. They live in the environment almost everywhere. Among them there are representatives of arachnids that are completely harmless to humans. But there are also poisonous ones, and even those that parasitize on the human body, simultaneously carrying various infectious diseases.
General characteristics of the arachnid class
The characteristic features of the structure of arachnids are associated with their adaptability to life on land. Representatives of the class belong to land arthropods with eight pairs of limbs.
Arachnids have a body consisting of two sections. At the same time, its connection can be represented either by a thin partition or by a tight bond. This class lacks antennae.
In the front part of the body are such limbs as oralorgans and walking legs. Arachnids breathe with the help of lungs and trachea. The organs of vision are simple. Some species are completely absent.
The nervous system is represented by nerve nodes. The skin is hard, three-layered. There is a brain, consisting of anterior and posterior. The circulatory organs are represented by the heart in the form of a tube and an open circulatory system. Arachnids are dioecious.
Arachnid Ecology
Arachnids were the first insects to adapt to life on land. They can be both diurnal and nocturnal.
The arachnid class is quite extensive, so if we talk about the habitat, then its representatives are found throughout Russia. Some insects feed on catching prey in the webs they have woven, others simply attack. "Hunters" from this class mostly feed on insects, but some bite people and animals, thereby causing various diseases. Some representatives prefer to live on the body of a person or animal, while others parasitize exclusively on cultivated plants.
Class overview
Scientists-zoologists conventionally subdivide the arachnid class into several orders. The main squad are spiders, scorpions, ticks, salpugs.
Scorpion Squad
Scorpion is an atypical spider, which is why it is placed in a separate detachment.
Arachnids of the "scorpion" type are small, no more than 20centimeters. His body consists of three well-defined sections. On the front there are two large eyes and up to five pairs of small lateral ones. The body of a scorpion ends with a tail in which a poisonous gland is located.
The body is covered with a thick and hard covering. A scorpion breathes with the help of lungs. They chose an area with a warm and hot climate as their habitat. At the same time, scorpions are divided into two subspecies: living in humid areas and in dry places. The attitude to air temperature is also ambiguous: there are subspecies that prefer a warm climate and high temperatures, but some tolerate cold very well.
Scorpions get food in the dark, they are distinguished by increased activity in the hot season. The scorpion detects its prey by detecting the oscillatory movements of a potential victim.
Scorpion breeding
If we talk about which arachnids are viviparous, then it is scorpions that for the most part bear offspring. However, there are also oviparous ones. The growth of embryos located in the body of the female is a rather slow process, and pregnancy can last more than a year.
Babies are born already in the shell, and after birth they immediately stick to the mother's body with the help of special suction cups. After about 10 days, the brood breaks away from the mother and begins to exist separately. The period of growing up in small individuals lasts about one and a half years.
The poisonous tail of a scorpion is an organ of attack and defense. True, the tail is not alwayssaves its owner from predators. Some animals know how to avoid blows, and then the predator itself becomes food. But if the scorpion nevertheless stung the victim, then many small invertebrates die almost immediately from the injection. Larger animals can live a day or two.
For a human being, the aggression of a scorpion does not end in death, however, in modern medicine, cases with very serious consequences have been recorded. A swelling occurs at the site of the lesion, which can be quite painful, and the person himself becomes more lethargic and may experience attacks of tachycardia. After a couple of days, everything goes away, but in some cases, the symptoms persist for a longer period.
Children are more sensitive to the effects of scorpion venom. There have also been cases of death among children. In any case, after an insect bite, you should immediately seek qualified help from a medical facility.
Solpuga Detachment
Recall that we are considering the class Arachnids. Representatives of this order are widely distributed in countries with a warm climate. For example, very often they can be found on the territory of the Crimea.
Different from scorpions by a large dismemberment of the body. At the same time, the hard jaws of the salpuga perform the function of catching and killing the victim.
Salpugs have no poisonous glands. Attacking a person, salpugs damage the skin with sharp jaws. Quite often, infection of the wound occurs simultaneously with the bite. The consequences are: inflammation of the skin at the site of injury, accompanied by pain.
Thisthere was a characteristic of arachnids, a salpuga detachment, and now consider the next detachment.
Spiders
This is the most numerous order, numbering more than 20 thousand species.
Representatives of different species differ from each other only in the form of the web. Ordinary house spiders, which can be found in almost any home, weave a web that resembles a funnel in shape. Poisonous class members create a web in the form of a rare hut.
Some spiders do not weave webs at all, but lie in wait for their prey, sitting on flowers. The color of the insects in this case is adapted to the shade of the plant.
Also in nature, there are spiders that hunt for prey by simply jumping on it. There is another, special category of spiders. They never stay in one place, but constantly move in search of prey. They are called wolf spiders. But there are also ambush hunters, in particular the tarantula.
Building a spider
The body consists of two sections connected by a partition. In the front part of the body are the eyes, under them are hard jaws, inside of which there is a special channel. It is through it that the poison from the glands enters the body of the caught insect.
The organs of sensitivity are tentacles. The body of the spider is covered with a light but durable cover, which, as it grows, is shed by the spider, in order to be replaced later by another.
There are small growths on the abdomen-web-producing glands. The threads are initially liquid, but quickly become solid.
The spider's digestive system is rather unusual. Having caught the victim, he injects poison into it, with which he first kills. Then gastric juice enters the body of the victim, completely dissolving the insides of the caught insect. Later, the spider simply sucks out the resulting liquid, leaving only the shell.
Breathing is carried out with the help of the lungs and trachea located in the front and back of the abdomen.
The circulatory system, like all representatives of arachnids, consists of a heart tube and an open circulation. The nervous system of a spider is represented by nerve nodes.
Spiders reproduce by internal fertilization. The females lay eggs. Subsequently, small spiders appear from them.
Pincer Squad
The order Ticks includes small and microscopic arachnids with an undivided body. All ticks have twelve limbs. These representatives of arachnids feed on both solid and liquid food. It all depends on the species.
Ticks have a branched digestive system. There are also organs of the excretory system. The nervous system is represented by the nerve chain and the brain.
Ticks reproduce by laying eggs. Representatives of the class are heterosexual. Their life expectancy reaches six months, no more. But there are also real centenarians.
Ticks, like spiders, live everywhere: in houses, gardens, fields. Some representativescan cause significant damage, damaging plants and grain. Quite often, ticks are carriers of serious diseases.
Characteristics of some representatives of the class Arachnids
Spiders of some species do not use nets when hunting. Among them is the sidewalk spider. The hunter waits for prey, hiding on a flower petal. The greenish-yellow color of the shell almost exactly repeats the color of the sepals, helping the spider to disguise itself. Not even the bees can see it. The spider attacks the victim at the moment when the insect lowers its head into the stamens.
Here is another characteristic of arachnids (Ticks order). Consider the taiga tick. He chose the Far East as his habitat, but is also found in the European part of the country.
The size of the male is about 2 mm, while the females are almost twice as large. The larvae actively parasitize small animals, but as they grow, the host also changes. The tick moves already on hares or chipmunks. Sufficiently developed and strong individuals choose cattle as victims.
The mouth apparatus, like all representatives of the class, is located in front of the body and is represented by a proboscis and strong sharp teeth. With their help, the tick is held on the body of the victim until it is completely saturated.
This was a brief description of some representatives of the arachnid class.
We hope you find the information useful.
