Insects

Common Cross (Spider): description, habitat

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The cross spider is a spider with white or light brown specks located on the upper part of the abdomen in the shape of a cross. The spider belongs to the order, the suborder are araneomorphic spiders, the orchoptera family (lat. Araneidae), the genus Crosses (lat. Araneus). The name of the spider was due to its color.

Photo by Didier Descouens

Where does the cross spider live?

Spider crosses are widely distributed throughout the temperate and tropical climatic zone of the globe. Krestovik species are found in Europe, Russia, Africa, in North America, in Asian countries. Most spiders lodge in moist, low-lying places near water bodies, in forests, parks, and gardens — wherever trees grow, between whose branches it is convenient to weave fishing nets. Often the round spider web can be seen in the window and door openings, as well as under the roofs of neglected buildings.

Photo author: Geri-oc

Cobweb spider cross.

The krestovik spiders weave a new web almost daily, because the old one very quickly comes into disrepair because of the gaps created by hitting the net of both small prey and large insects unsuitable for eating. Krestovik weaves his web at night, guided in the dark by a well-developed sense of touch. This behavior is fully justified: insectivorous birds, the main enemies of spiders, are already asleep, and the host of the nets is almost imperceptible in the dark. By morning, the fresh fishing net will be completely finished.

The cross spider weaves a network with a strictly defined number of radii and spirals, and the gaps between the turns of the adhesive thread are always the same. Such automatism is laid at the genetic level, so it is not surprising that young individuals are able to weave a fishing net no worse than adults. Young males build trap nets only until they reach puberty, and after they wander in search of a pair. Therefore, the males eat little and grow poorly, which explains the pronounced sexual dimorphism of the spider-krestovikov.

Photo by: Jodeli

What feeds spider tustovik?

Flies, mosquitoes, small grasshoppers, aphids and gnats that make up the basis of the ration of the spider's spider come across in the spider's web. During the day, an adult female can eat an amount of food equal to her own weight. When a very large or poisonous insect gets entangled in the nets, the spider immediately cuts off the threads surrounding the object that is not suitable for consumption. Flies and wasps capable of laying their eggs on living creatures, the crosses are wary and try to avoid. In the opposite case, winged insects descend from the top of the spider and lay, which is a favorable environment for the development of their larvae.

During the hunt, the krestovik sits in the center of the web or in the shelter of foliage located nearby. The vibration of the filaments is instantly caught by sensitive hairs, and the cross with its poisonous chelicera kills the victim, and then pours digestive juice into it so that the prey is digested. Only after this the spider-krestovik eats its prey.

Photo by: Jürgen Howaldt

Is the crosshair dangerous for humans?

The crucian spider venom contains hemotoxin and neurotoxin, deadly to invertebrates and small vertebrates. For humans, cattle, horses and sheep, poison is not dangerous, and the bite of the cross can not even be noticed. Sometimes in the place of the bite there is a slight, quickly passing pain. Moreover, the spider itself never attacks first, but bites a person or animals by chance if they stumble upon its web.

General characteristics. External structure

Spider-krestovik can be found in the forest, the park, on the window frames of village houses and villas. Most of the time, the spider is sitting in the center of its trapping web of gluey cobwebs.

The spider body consists of two sections: a small elongated cephalothorax and a larger spherical abdomen. The abdomen is separated from the cephalothora by narrow constriction. Four pairs of walking legs are located on the sides of the cephalothorax. The body is covered with a light, strong and rather elastic chitinous cover.

The spider periodically sheds, dropping chitin cover. At this time, it grows. At the anterior end of the cephalothorax there are four pairs of eyes, and below the pair of hook-like hard jaws is a chelicera. They spider grabs his victim.

Inside there is a canal. On the channel poison from the poisonous glands located at their base enters the body of the victim. Next to the cheliceres are the short, covered with sensitive hairs, the organs of touch, the knuckle.

At the lower end of the abdomen there are three pairs of spider webs that produce webs - these are modified abdominal legs.

The liquid released from the web of warts instantly hardens in the air and turns into a strong web of thread. Different parts of spider warts secrete different types of spider webs. Spiderwebs vary in thickness, strength, adhesiveness. Spider uses different types of cobwebs for building a fishing net: at its base there are more durable and non-sticky threads, and concentric threads are thinner and sticky. The spider uses a web to strengthen the walls of its shelters and to make egg cocoons.

Digestive system

The digestive system of the spider consists of the mouth, pharynx, esophagus, stomach, intestine (front, middle and back). In the midgut, long blind outgrowths increase its volume and suction surface.

Undigested residues are expelled through the anus. Spider can not eat solid food. Having caught the prey, (some kind of insect), with the help of a web, he kills it with poison and lets in his body digestive juices. Under their influence, the contents of the caught insect are liquefied, and the spider sucks it. From the victim remains only an empty chitinous shell. This method of digestion is called extraintestinal.

Circulatory system

The circulatory system of the spider is unlocked. The heart has the appearance of a long tube located on the dorsal side of the abdomen.

Blood vessels flow from the heart.

In a spider, the body cavity has a mixed nature - during development, it occurs when the primary and secondary body cavities join. Hemolymph circulates in the body.

Respiratory system

Spider respiratory organs are lungs and tracheas. Lungs, or lung sacs, are located below, in front of the abdomen. These lungs evolved from the gills of distant ancestors of spiders that lived in water.

In the spider-krestovik two pairs of unbranched trachea - long tubes that deliver oxygen to organs and tissues. They are located in the back of the abdomen.

Excretory system

The excretory system is represented by two long tubes - malpighian vessels. With one end the malpighian vessels blindly end in the body of the spider, the other opens into the posterior part of the intestine. Through the walls of the malpighian vessels, hazardous waste products come out, which are then brought out. In the intestine is the absorption of water. Thus, spiders save water, so they can live in dry places.

Reproduction. Development

Fertilization in spiders is internal. The female krestovik spider is larger than the male. The male transfers spermatozoa into the female's sexual opening with the help of special outgrowths located on the front legs.

She lays eggs in a cocoon, woven from a thin silky web. Cocoon weaves in various secluded places: under the bark of stumps, under stones. By winter, the female of the krestovik spider dies, and the eggs overwinter in a warm cocoon. In the spring from them young spiders leave. In the fall, they release cobwebs, and on them, as on parachutes, they are carried by wind over long distances - spiders are settled.

Structural features

The male cross has dimensions within 8-10 mm, females are larger - 15-25 mm. The insect has four pairs of eyes, each of which looks the other way and provides the spider with a fairly wide range of views. Despite this, the crucifiers see poorly, they are short-sighted and are able to distinguish only shadow, movement, and outlines of objects. But have a keen sense of smell and taste. The body of the spider is covered with hairs, which sensitively catch any vibration and vibration.

Krestovik ordinary has eight legs, the abdomen has a rounded shape, it is visible white or light brown spots in the form of a cross. Long thin paws end with three claws.

Insect behavior

How does the hunt happen? When an insect hits a spider’s web, the network vibrates and, as it approaches the victim, it kills it with the help of poison. Then she wraps the victim in thin threads, which she pulls from her abdomen with a pair of legs.

After that, the crosshead snacks on the threads that hold the victim, and moves to the center of the web for a meal. With the help of digestive juices, which the spider injects into its prey, it is digested under its own shell. The spider can only suck the semi-liquid contents and throw away the skin of the eaten insect. A spider can eat dozens of insects at a time. Dangerous spiders only for insects, their poison does not cause harm to humans.

Insect use

Krestovik ordinary is useful in that it destroys a large number of insect pests.

In ancient times, cobwebs were able to make clothes and jewelry. The French learned to make gloves and stockings out of it. But such production did not take place on a large scale, since for this purpose many insects would have to be fed and fed, which was not possible.

Web properties are used in optical devices where thin fibers are used. It is also needed in microbiology.

The network of the krestovik can be used as a disinfecting and antibacterial agent for wounds due to its ability to destroy many bacteria and not harm the animal cells. But do not use this method at home, as there is no confidence in the purity of the web used.

The cross spider is an extremely useful insect for humans and is not dangerous, although poisonous. The biggest nuisance that a cross bite can turn into is a red spot on the skin.

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