Class Arachnids today has more than 35 thousand different species. They live in the environment almost everywhere. Among them there are representatives of arachnids completely harmless to humans. But there are also poisonous, and even those that parasitize on the human body, while simultaneously transferring various infectious diseases.
General characteristic of the class of arachnids
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.
Representatives of arachnids have a trunk consisting of two sections. At the same time, its connection can be represented either by a thin partition, or by a tight bond. Antennae for representatives of this class are absent.
In the front of the trunk are extremities such as the mouth organs and walking legs. Arachnids breathe with the help of the 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-layer. There is a brain consisting of anterior and posterior. Circulatory organs are represented by the heart in the form of a tube and an open circulatory system. Arachnids belong to dioecious individuals.
Ecology of arachnids
It was the arachnids that became the first insects that had mastered life on land. They can lead both a daytime and a nightly active lifestyle.
The arachnid class is quite extensive, so if we talk about the habitat, its representatives are found throughout Russia. Some insects feed on catching prey in the networks they have woven, while others simply attack. The "hunters" from this class for the most part eat insects, but some inflict bites on people and animals, 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 ones are squad spiders, scorpions, ticks, salpugs.
Scorpion squad
Scorpio is an atypical spider, which is why it is allocated in a separate squad.
Arachnids of the scorpion type are small, not more than 20 centimeters. His body consists of three well-defined departments. In the anterior are two large eyes and up to five pairs of small lateral eyes. The body of the scorpion ends with its tail, in which the poisonous gland is located.
The body is covered with a thick and hard cover. Scorpion breathes with the help of the lungs. They chose the environment with a warm and hot climate as their habitat. At the same time, scorpions are divided into two subspecies: living in wet areas and in dry places. The attitude to air temperature is also ambiguous: there are subspecies that prefer a warm climate and high temperature, but some tolerate cold well.
Scorpions are fed in the dark, they are distinguished by increased activity in the hot season. The scorpion discovers its prey, capturing the oscillatory movements of a potential victim.
Scorpion breeding
If we talk about which arachnids are viviparous, then it is precisely the scorpions that mostly bear offspring. However, there are oviparous. The growth of the 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 are immediately attached 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 growing period in small individuals lasts about a year and a half.
The scorpion's poisonous tail is an organ of attack and defense. True, the tail does not always save its owner from predators. Some animals can avoid blows, and then the predator himself becomes food. But if the scorpion nevertheless stings the victim, then many small invertebrates almost immediately die from an injection. Larger animals can live a day or two.
For a person, 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 becomes more lethargic and may experience tachycardia attacks. 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. Among the babies, there were recorded cases of death. In any case, after an insect bite, you should urgently seek qualified help at a medical institution.
Solpugi squad
Recall that we are considering the class Arachnids. Representatives of this detachment are widely distributed in countries with a warm climate. For example, very often they can be found in the territory of Crimea.
They differ from scorpions in a large dissection of the body. In this case, the solid jaws of the salpuga perform the function of catching and killing the victim.
The salpug lacks poisonous glands. Attacking a person, salpugs damage the skin with sharp jaws. Quite often, wound infection occurs at the same time as a bite. The consequences are: inflammation of the skin at the site of damage, accompanied by pain.
This was a characteristic of the arachnids, the Salpuga detachment, and now consider the next detachment.
Spiders
This is the most numerous detachment, numbering more than 20 thousand species.
Representatives of different species differ from each other solely in the form of a web. Ordinary house spiders, which can be found in almost any house, weave a web in the shape of a funnel. Poisonous members of the class create a web in the form of a rare hut.
Some spiders do not weave a web 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, simply jumping on it. There is another, special category of spiders. They never remain in one place, but constantly move in search of prey. They are called wolf spiders. But there are hunters who attack from an ambush, in particular, a tarantula.
Spider structure
The body consists of two departments connected by a partition. In the front 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 captured insect.
The organs of sensitivity are the tentacles. The body of the spider is covered by a light but strong cover, which, as it grows, is discarded by the spider, and then replaced by another.
On the abdomen are small growths-glands that produce a web. Initially, the filaments are liquid, but quickly become hard.
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 victim’s body, completely dissolving the insides of the captured insect. Later, the spider simply sucks the resulting fluid, leaving only the shell.
Breathing is carried out using the lungs and trachea located in the front and back of the abdomen.
The circulatory system, as in all representatives of arachnids, consists of a heart tube and open circulation. The nervous system of the spider is represented by nerve nodes.
Spiders breed by the method of internal fertilization. Females lay eggs. Subsequently, small spiders appear from them.
Squad Mites
Ticks include small and microscopic arachnids with an undivided body. All ticks have twelve limbs. These arachnids feed on both solid and liquid foods. It all depends on the species.
The digestive system of ticks is branched. There are also organs of the excretory system. The nervous system is represented by the nerve chain and the brain.
Ticks multiply by laying eggs. Representatives of the class are heterosexual. Their life expectancy reaches six months, no more. But there are real centenarians.
Ticks live, like spiders, everywhere: in houses, gardens, fields. Some representatives are capable of causing significant harm, damaging plants and grain. Quite often, ticks are the carriers of serious diseases.
Characteristics of some representatives of the class Arachnids
Some species of spiders do not use webs during hunting. These include a side-walker spider. A hunter is waiting 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. Even bees are not able to notice him. The spider attacks the victim at the moment when the insect lowers its head into the stamens.
Here is another characteristic of arachnids (Squad Mites). Consider a 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. Larvae actively parasitize on small animals, but as they grow, the “host” changes. The tick is already moved to hares or chipmunks. Sufficiently developed and strong individuals choose cattle as a victim .
The oral apparatus, like all members 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 victim’s body until it is completely saturated.
This was a brief description of some arachnids.
We hope you find the information useful.