Legs of arachnids - description, structural features and quantity

The legs of arachnids have a very complex structure and a unique structure; they consist of a large number of different segments and are attached to the cephalothorax. All limbs end in a paw, thanks to which arthropods can move and hold securely on any surface. In certain varieties, the chelicerae and pedipalps are highly developed.

Number of legs in spiders

The spider has 8 legs, but we must not forget that the class of arachnids includes about 40 thousand species, divided into 3 subspecies. They all differ in lifestyle, appearance and size. Their body has 2 parts: the belly and the cephalothorax, which are connected by a small tube.

The spider's legs are covered with small villi; on the foot of one leg there can be up to 3 thousand of them. The abdominal limbs are located on the cephalothorax. There are spines at the end of all legs, with the help of which the spider easily moves along the web. Between the spines there is a claw-shaped appendage; in certain varieties there is a claw instead. The legs consist of various segments:

• hip and knee area;
• trochanters;
• paws;
• shins;
• heel and pelvis.

The claw part is not a true segment, since in certain animals it is not separated from the tarsus. The hind and front legs are the largest. The second pair is the shortest, the third has an average length.

In many species, the approximate size of the legs is about 3 cm, in others it varies between 20-40 cm. There are species of arachnids that catch their prey with the first and second pair of limbs, because they are more developed and can be longer than others. The size of the spider's legs will depend on the place of residence and lifestyle characteristics. Apart from movement, the limbs do not perform any other functions, therefore they are walking. Taking into account the species, the size of the spider can vary between 0.3-12 cm, and the paw span can be up to 40 cm.

Having considered how many legs a spider has, it should be noted that their number differs from the number of legs in insects. Arachnids have 8, insects have 6. All have 6 joints. When counting, it turns out that they have 48 tribes.

Complex mouthparts

The oral cavity of arachnids is equipped with chelicerae; as already mentioned, this is the first pair of head limbs in arthropods. What are they needed for? Since they are an integral part of the oral apparatus, their main task is to crush, grind or pierce food. The appearance depends on the type of animal; chelicerae can look like claws, hooks or needles. These features depend on the type of oral cavity.

Here are some types of oral apparatus:

• Gnawing (barn mites). The chelicerae are large and claw-like.
• Piercing-sucking (ticks whose diet includes plants or animal blood). Chelicerae, accordingly, have a thinner shape, without teeth, resembling a hollow tube.

In spiders, chelicerae have a claw-shaped end segment on which the venom gland duct opens.

Difference from insects

The spider belongs to the class of arachnids, it is not an insect . Characteristic features of this type:

1. The main difference between arachnids and insects is that the last 6 legs are located on the chest, and not on the cephalothorax. In addition to external differences, animals have different structures of internal organs.
2. Centipedes are also not insects, since they belong to a separate species.
3. If we compare the body structure of arachnids with other creatures, it can be more closely related to a scorpion.

Spiders that live in apartments cannot harm the human body. You need to pay attention to sanitation conditions. Animals live in houses where there is enough food to remove them, it is necessary to get rid of the main cause of the invasion.

Number of legs in arachnids

Many classify this class as insects due to their appearance and small size. But in fact they are arachnids. In order not to make mistakes, you need to know the structural features of the spider’s legs and how many of them the spider has. This species has 12 legs, but not all of them are walking, but only four pairs.

Almost all arachnids are predators. This determines the structure and number of legs. The body can be divided into 2 main parts:

• cephalothorax;
• abdomen.

On the cephalothorax there is a mouth, eyes, 4 pairs of walking legs and 2 additional pairs, which are located above the mouth opening. They are called chelicerae. These legs have one fixed segment covering the fangs. Often, the fangs contain channels designed to inject venom into the victim’s body. After the chelicerae come the pedipalps, which are needed for spatial orientation.

Next are the abdominal limbs. In arachnids, they are the ones that walk. These are long paws that are easy to stay above the ground. Also, their structure allows spiders to jump high (compared to their body size) and run fast.

Scientists conducted many experiments. Experiments have shown that with the loss of one limb, the spider completely retains its mobility. He is also good at hunting and weaving webs. But already without three legs, the death of the arthropod occurs.

The main purpose of the paws

All spiders have limbs that perform the same function, and it makes no difference what species the individual belongs to. They move using their walking paw, which is their main one. The method of movement and speed of arachnids may differ, as it depends on the structure and size of the legs . The forelimbs help arthropods:

1. Determine whether the prey is suitable as food.
2. Grasp and hold the victim tightly.
3. Place your babies on the back and throw them out of there. Moreover, they throw children over very long distances.
4. Make a cocoon and create a web.
5. Resist attacks from predators.
6. Dig holes.
7. Move across the surface.

Small hairs on the legs help animals sense touch, learning about the external environment. With their help, they are well oriented in space, can hear sounds and smell. Before starting to move through unfamiliar territory, they first move their limbs in front of them, and only then move.

Limb functions

The main function of the legs is to provide the spider with the ability to move. The spider's record speed is 3.5 km per hour. The hairs that cover the paws are sensors. Some types of hairs are even sensitive to chemical elements. Others are able to “hear” the slightest vibration in the air, helping the spider prepare for the appearance of a prey or predator. The paws contain a complex chemical analyzer that can identify a large number of odors. These analyzers are very important for reproduction because they allow males to identify females of their species, detect and track their pheromone trail, and help them distinguish males from prey.

The front pair of limbs of the spider performs many functions: capturing and holding prey; determining the suitability of prey for food; weaving cocoons and webs; putting babies on their backs and throwing them off; movement on the substrate; digging a hole. Spiders use their front legs to fight predators.

Pedipalps and chelicerae

When counting how many legs a spider has, it is considered that arachnids have 10 legs. This is due to the pedipalps and chelicerae, which are located in front of the animal’s cephalothorax. They are quite long and look like paws. Their main task:

1. The pedipalps are the second pair of legs, consisting of several segments. On the head part there is a chewing outgrowth with which the spider grinds its prey. The rest resemble a tentacle.
2. Chelicerae are located near the mouth and have 3 parts that look like small claws. The outermost finger is movable. In certain species it has the shape of a claw or a pointed process, which consists of 2 parts. Due to this structure, the animal breaks through the prey's cover.

The task of the chelicerae and pedipalps is to grind prey, knead and chew it. Poisonous spiders, thanks to chelicerae, inject a toxic substance. When the victim dies, a certain amount of saliva is injected into it, after which the insides acquire a mushy consistency. The spider consumes the resulting pulp as food thanks to its sucking stomach. Fertilization of females occurs through the pedipalps.

Many arachnids may have fewer legs in their natural environment. They lose their legs in battles with predators, so for a full life, 6 limbs are enough for them, the eighth pair being a spare one. New paws do not grow in place of lost paws.

Sensitive Organs

Very important organs in arachnids are the chelicerae and pedipalps. The latter contain a large number of sensitive hairs, which respond especially quickly to various tactile irritations. These hairs are called trichobothria; in addition to the pedipalps, they are also found on the legs and the surface of the body. Trichobothria are needed to detect air vibrations.

In addition to the spider's chelicerae and pedipalps, there are other sensory organs - lyre-shaped organs for chemical sense and smell, as well as eyes, the number of which depends on the species. There can be 12, 10, 8, 6, very rarely 2. As a rule, spiders have four pairs of simple eyes, and of different sizes, some larger, others smaller.

Longest limbs

A rare species of giant spiders, Heteropod Maxima, lives in Asia. The span of its limbs can be more than 40 cm. This species lives in caves in the Khammouan region. Also long limbs have:

1. Hunter. The size of the limbs is more than 32 cm. This species can cover about one meter in a second. When it appears, a ticking sound is heard.
2. Goliath tarantula. Lives in the tropics of South America. The weight of the animal reaches 180 g, the size of the legs is 16 cm. It is the largest after Heteropod Maxim. The lifespan of males is no more than 7 years, females - up to 16 years.
3. Tegenaria. Lives in people's homes all over the world, limbs are 8−14 cm long.
4. Baboon giant. One of the types of tarantulas. Body length - up to 14 cm, legs - up to 22 cm.
5. Camel spider. It lives in the desert, can move at speeds of up to 3 km/h, defending itself from predators, and makes a squeaking sound, this distinguishes it from other species. Size - up to 9 cm, leg length - up to 32 cm. Belongs to the class of the phalanges suborder. Lives up to four years.
6. Nephila. These individuals are also known as the golden spider or tree spider. The length of females can reach up to 17 cm. They weave webs measuring more than one meter.
7. Crab spider. The paws of these individuals resemble the claws of a crab in appearance, which is why they received the corresponding name. Lives in the crevices of trees. The length is up to 26 cm, there are villi on the body, and spines on the limbs.
8. Colombian tarantula. Size including limbs - up to 25 cm. Lifespan of males - up to 4 years, females - up to 20 years.
9. Brazilian tarantula. Often kept at home as an exotic animal. The female’s weight is up to 120 g, size is 14 cm, limb length is up to 36 cm. Life time is about 29 years.

Neighborhood with people

Certain species of arachnids live close to humans. They live in places where there is enough food. As a rule, insects are eaten, but the diet will depend on the type of spider . The most common houses are:

1. Haymaker. Taking into account the subspecies, the length can vary between 3−12 mm. Moreover, his legs are 5 times longer than his body. It likes to make webs on windows, for which it is also called the window spider. To catch the prey, the animal needs to position itself upside down near the placed web. When prey becomes entangled in the net, the predator rushes towards it, bites it, and then injects poison.
2. Tramp. They enter the house by accident. These spiders do not set up webs; they catch prey on the move. When everything edible is destroyed, the arthropod leaves the house, moving on.
3. Brownie. This is a small yellow individual 6−12 mm long. There is a brown pattern on the body. Females are larger than males. Make a web in the form of a funnel.

Spiders appear in the house when there is high humidity and a large number of insects that rapidly multiply in these conditions and move from room to room: mosquitoes, fruit flies, beetles.

Amazing facts

The world of spiders is very diverse. These are unique and charming animals:

1. There is a separate subspecies of the spider family called phrynes. It includes approximately 60 individuals. They have certain characteristics, the main one being that they do not know how to weave a web. They have quite large legs, and the front jaws, intended for hunting, are very strong.
2. Spiders have no skeleton, only a hard shell. Because of this structure, the size of all arachnids is small. There are no large specimens that are shown in movies. Otherwise, the animal would have died under its own weight.
3. It has been proven that the web is stronger than steel and other metals that exist in the world. Scientists still cannot make it artificially.
4. The number of eyes in spiders can range from 2 to 12, and not 8, as many people think.
5. During the hunt, arthropods react to vibrations. They can be recreated using a violin. To lure the spider out of its hiding place, you just need to play the instrument.
6. The population of Cambodia keeps the tarantula spider as a pet, consuming the arthropod as food, as it is a magnificent delicacy.
7. All varieties of spiders make a web in the shape of a circle, and only the gladiator makes a square, and the web of the orb weaver can reach up to 8 m in size.

Most people are terrified of spiders. This fear is called arachnophobia. However, in reality, these small representatives of arthropods have much more reasons to be afraid of humans. Spiders are the most unusual animals living on Earth. They received such fame due to the features that nature gave them.

The structure of the web legs

The paws can be divided into 7 separate parts. All of them guarantee fast and agile movement. The legs themselves additionally have hairs responsible for sensitivity and study of the surrounding environment, determining whether the catch is edible or inedible. All parts of the foot guarantee perfect balance when moving along the web.

So, the standard structure of the tarsus includes the following segments:

• basin;
• trochanter;
• hip;
• cup;
• shin;
• forefoot;
• a foot, at the end of which there are additionally curved sharp claws for the ability to move along vertical surfaces or the ceiling. Some species use them to comb and straighten woven webs.

Foot sizes

The first, that is, the front pair of legs, differs from the remaining 3 pairs in most representatives of the arachnid family. This feature is due to the fact that it is the front legs that perform important functions for life support: movement and capture of the victim, which means this particular pair should be stronger than others.

Also among the differences for the two front legs, one can note the club-shaped shape in certain subspecies. The tarsi extend straight from the heel and form a clear angle in relation to the entire leg. This feature allows the first pair of limbs to be used as a tactile organ. The other 3 pairs are used for movement and are generally similar to each other.

Spider leg length

The size of the legs, namely such a parameter as length, directly depends on the type of habitat and lifestyle of the arachnid. The longest are the first and fourth pair of legs. Next in length is the second, but the third is the shortest.

The minimum length of the paw of an adult is about 0.5 mm, and the longest is 35 cm.

It should be noted that despite the almost identical length of the first and last pairs, in some subspecies the front ones will still be slightly larger. This feature is explained, as mentioned earlier, by the need to reliably capture and hold prey.

The main functions of individual parts of a spider's legs

Absolutely every spider has special sensitive hairs on its legs. They are responsible for the ability to perceive sound waves from the surrounding nature and help to recognize odors and the presence of obstacles on the way.

Sensing a potential victim with just one hypersensitive hair, the spider quickly moves towards it and plunges its fangs with a poisonous substance that slowly paralyzes and destroys the food it has obtained. The pedipalps are additionally involved in this process.

Another important element in the legs will be glandular tubules, which simultaneously produce an adhesive substance for weaving webs and cover the legs with a special composition that prevents the spider from sticking to its own web

For spiders that live in water, their legs are necessary to transport air bubbles under the water column, where they choose a secluded place to live.

Another important function is self-defense. Some species, when a dangerous object approaches, begin to comb off poisonous hairs from the abdominal region. When such a hair gets into the eye, it causes a severe burning sensation and in most cases the attacker retreats. Even after shedding, the hairs are restored, but this only happens when the subsequent molt begins.

As male spiders mature, bulbs or cymbiums appear at the ends of their legs, which are used to fertilize the female, who often eats her partner after the process is complete.