Structure and length
Each leg consists of 7 parts: 1) pelvic segment, 2) short trochanter, 3) long femoral part, 4) knee part, 5) tibia, 6) calcaneal segment and 7) tarsus, ending with 2 or 3 claws that are involved in manipulation of silk and displacement of spider web threads in networks. The claws also allow spiders to walk on the ceiling. Between the claws there is a pad with a sticky substance.
Usually the legs are more or less densely covered with adjacent or protruding hairs that act as sensors. Many spiders have hard bristles on the heel segment of the fourth pair of legs - this is a “comb” for the web. The spider's lifestyle dictates the thickness and length of its legs. The legs have different lengths: the front and back are the longest, the legs of the second pair are slightly shorter, and the shortest are the legs of the third pair. For most species of spiders, the average leg length is about 2 cm. For large species, it is from 15 to 35 cm. For example, the leg span of Heteropod Maxima (Laos) is over 30 cm, and Theraphos Blonda (South America) is 28 cm.
Difference from insects
The spider belongs to the class of arachnids, it is not an insect . Characteristic features of this type:
- 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.
- Centipedes are also not insects, since they belong to a separate species.
- 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.
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.
About arachnophobia
Science knows more than 40 thousand species of spiders. Some stand out for their size, others for their toxicity, and others for their color. But at the same time, for the majority, the appearance of absolutely all arachnids is unattractive, and some experience panic fear of them. Such people are called arachnophobes.
This is interesting! Statistically, the fear of spiders is much stronger than the fear of guns and flying in airplanes!
But why are people afraid of spiders?
After all, if you look at it, the arachnid has much more reasons to fear a person - he has much less chance of causing us any harm than we have in relation to him. Thus, the phobia itself seems somewhat irrational. There is a theory that the fear of spiders dates back 350 million years ago, to a time when humans did not yet exist. Fossil arachnids were mostly poisonous and posed a serious threat to primates. As a result, the latter developed a reflex of situational readiness - when a spider appeared, they were forced to hide with lightning speed. Over time, the number of deadly species became much smaller, but the instinctive fear remained. Thus, it turns out that arachophobia developed as part of human evolution.
This is interesting! Arachnophobia is unknown to some peoples, mostly uncivilized ones - some, including children, can stroke quite large spiders with complete ease, others even eat them!
Chelicerae and pedipalps
On the cephalothorax in front of the spider's mouthparts there are two chelicerae: these anterior appendages are not legs, although they are similar to them, and consist of a large rod and a movable hook, at the end of which there is a channel with poison. They are used primarily to bite, poison, and immobilize prey. Poison hooks inject a deadly substance into the victim. In other species lacking maxillary blades, this organ is also used to introduce digestive juices, which liquefy the inside of the insect and turn the contents into a “soup” that can be absorbed by the spider by suction. Also, with the help of chelicerae, the spider transfers prey and a cocoon.
Located next to the chelicerae, the pedipalps or “paws-jaws” play the same role as the antennae of insects. They are used to probe the immediate environment, sensory exploration of prey and processing it. Pedipalps, also called claws, are similar to walking legs, only very short, and also have 7 segments. In general, the function of the chelicerae and pedipalps is similar to the function of the teeth. The pedipalps in adult males also serve as a secondary reproductive organ.
A little about nutrition
Quite often, people are sincerely surprised and cannot understand what spiders eat in their apartment, where there are no insects. In this case, it is important to remember one thing - even if you are sure that no one lives in your house except you, the appearance of spiders always indicates the opposite.
If a spider came into your house and wove a web in it, it means that there is a victim nearby that can fall into it. You may not see these small insects, but at least someone definitely lives in any apartment (provided that you do not chemically disinfest it every week).
Spiders living in apartments are insectivores and eat almost everything with legs, antennae and wings:
- silverfish can live quietly under your bathroom;
- in the kitchen where there is a vase of apples, tiny fruit flies can settle;
- food pantries often contain various beetles that eat cereals, flour, etc.;
- in addition, it could be flies and mosquitoes, insect larvae and other spiders accidentally flying in from the street.
This is interesting! By eating insects, spiders bring us great benefits. And if the latter did not exist, then in the abundance of the former we would simply choke!
Why so many legs?
Scientists have discovered that spiders have more legs than they need. More than 10% of arachnids have at least one leg less. During the experiment, spiders were placed in plastic boxes in which they could spin webs. One half of the spiders had 8 legs, while the other half was missing one or more. Webs made by spiders that were missing at least one leg were not much different from those made by intact spiders. When scientists placed flies in plastic boxes, they discovered that spiders with six or seven legs could hunt and feed on insects. But there is a limit to the number of legs a spider can lose without harming its vital functions. Observations of five-legged spiders have shown that their webs are of very low quality.
Based on the data obtained, the researchers suggest that spiders have legs that they don’t really need, they are, as it were, spare ones. Spiders often lose limbs in fights with predators - wasps, mantises, birds. For a full life, a spider only needs three pairs of legs, which means the fourth pair is a spare one.
Why can't a spider get tangled in its web?
The spider trap system is almost perfect.
Their web consists of thin, but at the same time durable silk threads. They are assembled into a single fabric-type structure, consisting of complex geometric shapes and quite effective. The insect's web is treated with a special sticky organic glue that permanently immobilizes the prey. The spider itself moves along its web very quickly and its legs do not stick to it.
The thing is that only the circular threads are covered with biological glue, into which the victim gets caught. But the one who created the web moves only along threads not covered with glue.
In addition, biologists have found that the hairs located on the heel joints of insects are covered with a special substance that prevents them from sticking to the adhesive layer of the web. Scientists treated the spider's paws with a soap solution, and then alcohol, and placed the spider's web woven on it. To the surprise of biologists, the spider got stuck there because it had lost the protective layer on its legs.
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:
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.
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:
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.
