One of the most interesting topics for a 7th grade biology presentation is “The structure and behavioral features of the cross spider.” This arthropod is the most common species of all existing ones. His web can be found absolutely everywhere. To become more familiar with a unique representative of nature, students are advised to briefly outline its features in a report, message, or use diagrams.
general information
You can meet the common cross spider in almost every country. They live on all continents except northern and southern latitudes. In total, there are more than 40 thousand different species of arachnids in the world, 2 thousand of which are crosses. The territory of Russia can boast of only 10 species of these arthropods. They belong to the family of orb-weavers, a genus of araneomorphic spiders. They are most common in the areas:
- Rostov;
- Smolenskaya;
- Astrakhan.
Arthropods are very often found in the Mordovian region.
The size of cross spiders is quite small. But it is worth noting that the female of this species is larger in size. The length of the male is only up to 1.1 cm. His partner can reach 4 cm. The female and male sexes can be distinguished from each other by their abdomen. In males it is small and narrow, in females it is round and large. The external structure of the cross spider does not differ significantly from its relatives in its genus. At first glance, this is a completely ordinary spider, except for the peculiarities of its external color.
Habitat
This type of spider prefers temperate and tropical climate zones. Various types of cross can be found in countries such as:
- Russia.
- Asian countries.
- Countries of Europe.
- Africa.
- North America.
The cross spider feels comfortable in damp areas, near water, as well as in parks, gardens and forests. In other words, the crusader can be found wherever there are trees . After all, it is between the tree branches that the crusader weaves his web. The spider's orb web is found under roofs and in doorways of abandoned houses.
Appearance Features
Cross spiders differ from other species in their individual color. A distinctive feature of their appearance is a kind of cross, which consists of several light spots. Between themselves they form a mosaic. Drawings of cross spiders and their colors differ from each other in a variety of colors. Most often these are brown shades. The spider's body is well protected by a chitinous covering, which changes to a new one during molting.
A sign of arachnids is their structure. They consist of a cephalothorax and abdomen. These parts are connected by a constriction. The cephalothorax is equipped with an oral cavity, eyes and walking legs.
Despite the fact that crosses have 8 eyes, they cannot boast of good eyesight. They can only see the outline of an object. Since all pairs of eyes look in different directions, spiders have a wide view.
The hairs on the abdomen and pedipalps perform the function of touch. They clearly react to various stimuli, which helps him get a complete picture of what is happening. Hairs have different sensitivities. Therefore, each species plays its own special role.
Functions of touch hairs:
- some are capable of detecting sounds of different frequencies;
- others perceive vibrations and air movements;
- still others react to other external stimuli, including chemical ones.
Crosses have an excellent sense of smell. It helps to cover the lack of vision and perfectly navigate in space.
One of the important organs can be called chelicerae, jaws or a pair of limbs, which belong to the oral apparatus of the cross. The limbs are equipped with claws. They are important in the life of arthropods. The ducts of poisonous glands run from the head through the limbs. With the help of which the insect defends itself, captures and kills its prey.
In total, the cross has 6 pairs of limbs:
- pedipalps - 1 pair - recognizes and holds prey. They are located on the last segment of the body;
- walking limbs equipped with claws - 4 pairs;
- chelicerae - 1 pair.
In an adult male, the copulatory organ is located on the final segment of the pedipalps. Immediately before mating, it is filled with seminal fluid. The sperm receptacle is located on the female.
Reproduction. Development
Fertilization in spiders is internal. The female cross spider is larger than the male. The male transfers sperm to the female's genital opening using special outgrowths located on the front legs.
She lays eggs in a cocoon woven from a thin silky web. The cocoon weaves in various secluded places: under the bark of stumps, under stones. By winter, the female cross spider dies, and the eggs overwinter in a warm cocoon. In the spring, young spiders emerge from them. In the fall, they release cobwebs, and on them, like parachutes, they are carried by the wind over long distances - the spiders disperse.
Internal structure
The story about the cross spider involves a description of its internal structure. Special spider warts help him weave webs. They are located in the lower part of its abdomen. There are three pairs in total. They include almost 1 thousand special glands. The spider not only catches prey with trapping nets, they help equip its shelters and arrange cocoons for future offspring . It is worth noting that the web of the cross is characterized by increased strength.
The heart of the cross is located in the dorsal abdomen. It is an elongated tube on both sides of which there are quite large vessels. The respiratory system is located here in the abdomen. These are two lung sacs, consisting of many leaf-shaped folds filled with oxygen. The systematics of circulation of liquid hemolymph ensures its uninterrupted enrichment with oxygen.
The digestive system is located outside. The cross is unable to digest food on its own; the caustic digestive juice helps with this. It is this that the spider injects as soon as the victim dies. After some time, the insides under the chitinous shell of the prey turns into an easily digestible nutrient solution. Which the arthropod simply drinks.
The nervous system consists of many nerve vessels and nodes that connect the brain with all the senses and limbs. The abdominal nerve cord connects the brain to all internal organs. The brain is a cephalothoracic nerve ganglion.
This is interesting
- How do crusading spiders move along their own web, since its threads are covered with an adhesive substance? The fact is that this arthropod moves along radial threads on which there is no adhesive substance, so it does not stick.
- The web of the cross can show the composition of the air, which is why it is so actively used in microbiology.
- Spiders aren't the only ones who need webs. Thanks to the strong threads of the cross spider's web, some tropical residents use it to weave jewelry, fishing gear, and also to make fabrics.
Behavior in nature
The lifespan of a spider of this species is short. On average, according to statistics, an adult lives up to 1 year . In rare cases, up to 2 years. The natural habitat constantly exposes the crosses to danger. They have many enemies in nature, from birds to parasitic flies. Which are capable of laying their eggs directly in the body of the cross. Spiders do not tolerate bright sun, so they can mainly be found in shady places.
Surprisingly, few people know that such small arthropods as spiderworts are capable of traveling long distances. Thanks to their web, they roam from one structure to another. And if they have a favorable wind, they can glide across their networks for distances of up to 400 km.
An interesting fact is that inside its web, the spider does not stick to it. This is explained by the fact that it moves exclusively along dry threads, and not along sticky ones. In addition, it has been proven that web weaving in spiders is developed at the genetic level. This is explained by the fact that a young spider can weave its masterpiece no worse than an experienced adult spider.
For whom is the cross spider dangerous?
Crusader venom contains substances such as hemotoxin and neurotoxin, which are fatal only to invertebrates, as well as small vertebrate organisms. For humans, cattle, sheep and other living organisms, the bite does not pose any particular danger, and some do not even notice it. The site of the bite can be recognized by slight pain, which passes very quickly. Spiders never attack a person first, but bite only in case of defense, if the web was accidentally touched.
Puberty and mating
Throughout the spring and summer, young males are mainly busy getting food for themselves and constantly weaving new webs. Such hunting guarantees them adequate nutrition. When the time comes for puberty, they leave their shelters and go in search of a female. While searching, they feed sparingly, which may explain the significant difference in weight category between males and females during the mating season.
Attracting a female is through mating games. To attract the attention of the female, the cross-tailed spider swings its web and dances at the same time. Mating involves the transfer of seminal fluid from the male's pedipalps to the female. After transferring the seed, the spider tries to hide as quickly as possible. But not many people succeed in this. Most of the crosses die from the poison of the female.
Reproduction of arachnids
All arachnids are dioecious. The female cross spider lays eggs in the fall in a cocoon woven from a silky web, which she places in secluded places (under stones, stumps, etc.). By winter, the female dies, and spiders emerge from eggs overwintered in a warm cocoon in the spring.
Other spiders also take care of their offspring. For example, a female tarantula carries her young on her back. Some spiders, having laid eggs in a web cocoon, often carry it with them.
Among the arachnids there are species whose poison is dangerous for humans and farm animals (karakurt, scorpion), human parasites (itching itch) and mites that carry pathogens that are painful to humans and animals (taiga tick, etc.).
Food and hunting
Spiders of this classification are predators. They lead a dual lifestyle. They usually hunt during the day and evening, and at night they repair nets and build new ones. Since this activity is unsafe during the day, spiders are waylaid by birds and other enemies. They actively obtain food for themselves depending on their habitat . Their diet mainly includes:
- flies;
- mosquitoes;
- butterflies;
- aphid.
In other regions, their diet is supplemented by midges, other insects, and sometimes even small animals. Surprisingly, not all insects can be included in the diet. If an uninvited guest with an unpleasant odor, an individual of impressive size, or a poisonous insect is caught in the web, the spider releases it, biting its webs.
During the hunt, the crossfish freezes in the very center of the web. From the outside it seems that the hunter is dead. When prey gets caught in the net, the crossfish reacts with lightning speed. The victim automatically becomes entangled in the net. At the same second, a hunter approaches her and plunges poisonous claws into her body. The prey is instantly paralyzed. The hunter can enjoy the delicacy here and now, or leave the prey in reserve.
The cross has a wonderful appetite. Every day he absorbs an amount of food approximately equal to his body weight. At one time he is able to eat more than 10 different insects. Therefore, he devotes most of his life to obtaining food. The crossman devotes little time to rest. After all, even when he is tired, the hunting signal thread tied to his leg will always notify him of the caught victim.
Arthropod lovers very often keep crosses as pets. Due to their behavioral characteristics and ease of care, spiders quickly reproduce in captivity. Most importantly, for this they need to be provided with a spacious terrarium. Since they weave webs of quite impressive size. It is worth noting that the bite of the cross spider is not dangerous for humans, so those who consider it poisonous can safely reconsider their point of view.
Poisonous or not crusader
The poison is toxic to invertebrates and vertebrates. It has an effect on the body of rats, mice, humans, and rabbits. Sheep, horses, guinea pigs, and dogs are resistant to poison. For insects and invertebrates, a crusader attack is fatal. Animals experience temporary deterioration in well-being and external irritation.
The Crusader is not dangerous to humans. When it sees people, the spider tries to hide unnoticed. However, if there is a threat to its own life, it can bite. There are 2 small spots left on the body. Initially there is pain and burning. The next day, suppuration occurs. In people with weakened immune systems and children, their overall health deteriorates afterward. Weakness, nausea, headache, dizziness, and abdominal discomfort appear. The condition returns to normal in a few days.
The common cross can be found throughout Europe. Its favorite habitats are forests, bushes, and gardens. Typically, crosses can be seen at a height of about 30-150 cm above the ground. The cross spider loves damp places where there are a lot of mosquitoes and flies - the favorite food of this spider. However, such habitats often pose a certain risk for the spider.
That is why many crosses are generally in the crowns of trees at a height unattainable for enemies. They build themselves a secluded shelter from leaves, stretching their web between. By the way, wheel-shaped webs can often be seen under the eaves of abandoned architectural buildings, as well as in the window frames of your own home. Since the web is an integral attribute of the life of the cross spider, its existence without it is simply impossible.
What to do if you are bitten
The spider bite is not fatal to humans, cattle, horses, dogs, sheep, the danger exists only for rats, rabbits and mice.
Usually, the spider bites a person by accident if he falls into a web where a hunter is waiting for his prey. Its poison is a colorless, cloudy and viscous liquid.
Preventing a Bite
To avoid a spider bite, you should follow some simple recommendations:
- When going to bed in nature, be sure to close the entrance to the tent at night;
- Before going to bed, carefully examine your bed, clothes and shoes;
- be careful near the webs, remember that there is a cross nearby that is waiting for the victim;
- be careful during country and garden work;
- be vigilant when in abandoned old premises;
- If you find a cross, do not try to pick it up.
Symptoms
The cross spider is able to bite through only the thinnest skin. The pain of the bite is comparable to that of a bite; a person feels a prick with a thin needle, and sometimes does not notice anything at all.
A white spot with red or pink edges, small in size (no larger than a five-kopeck coin), appears at the site of the lesion.
The main signs of a spider bite that develop after 5-20 minutes include:
- irritation at the site of injury;
- aching joints;
- weakness;
- skin redness;
- slight chills;
- subcutaneous hemorrhages;
- slight increase in temperature;
- edema;
- hardening of the skin;
- headache;
- burning.
First actions after a bite
If you are bitten by a cross, the following actions should be taken:
- wash the affected area with running water and soap to eliminate the risk of infection;
- Apply ice or a cold compress to the bite site;
- if you have a fever or headache, it is recommended to take paracetamol;
- If you have an allergic reaction, take any antihistamine that does not require a prescription.
If there is a rapid increase in symptoms or a child has been bitten, it is recommended to seek help from a doctor.
Consequences
The cross releases epeirotoxin
, which is absorbed and completely eliminated from the human body within 24 hours. There may be slight swelling at the site of the bite for several days.
If there is no improvement in the person’s condition, the following actions should be taken:
- apply cold to the affected area;
- use anti-inflammatory ointments: Sinaflan, Kremgen;
- Lubricate the area with alcohol.
Do not scratch the site of a spider bite. This can lead to the development of a purulent process when infection enters the skin.
It makes no sense to burn or cut the skin when bitten; it does not have serious consequences. This is just additional trauma.
To date, not a single fatality has been reported from a cross bite. But in some cases, after recovery, soft tissue necrosis is observed at the affected area.
Exercise caution when out in nature. Remember that a cross spider will never attack a person on its own. Do not provoke a bite, and if affected, take measures to prevent complications from occurring.
Do not provoke a bite, and if affected, take measures to prevent complications.
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