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· 29 Jan 2022

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How many legs does a Spider have?

Do you feel scared when you see a spider hanging in air with almost an invisible thread it forms? But in reality, spiders are helpful because they eat insects, which keep bug numbers in check. Spiders are fascinating organisms and one of the easiest families of invertebrates to observe. Despite the fact that this kind of arachnid can be terrifying to certain people, especially those who suffer from arachnophobia, they are fascinating creatures.  Let us understand what sets spiders apart from other creatures and How many legs does a spider have?

Spiders – The Arthropods
Spiders are arthropods belonging to the Arachnida class, with eight legs and fangs capable of injecting venom. They have established permanent colonies in every habitat except sea and air, and they can be found on all continents except Antarctica. Spiders are distinguished from insects by the absence of antennae and the presence of an extra set of legs. Although most spiders are harmless or only bite humans in non-lethal ways, some species, such as recluse spiders, wandering spiders, and widow spiders, possess venom which is poisonous enough to kill an adult human being. The majority of spiders are carnivorous, feeding on other spiders and insects.

Characteristics of Arthropoda
The following are the features of Arthropoda:
1.    The body is triploblastic, segmented, and symmetrical on both sides.
2.    The head, thorax, and abdomen are the three parts of the body.
3.    They have jointed appendages on their bodies that aid in mobility.
4.    They have an open circulatory system
5.    There are two compound eyes on the head.
6.    Chitin makes up the exoskeleton.
7.    Arthropods on land excrete through Malpighian tubules.
8.    They are unisexual, with either external or internal fertilisation.
9.    Their digestive system is well-developed.
10.    They breathe through the trachea or the general body surface.

Legs and Locomotion
Spiders, like other members of the Arachnida class, have four pairs of limbs, totalling eight legs. Spiders employ hydraulic pressure to move and stretch their legs. In a spider's leg, the only extensor muscles are found in the hip joint. As a result of the perforated cephalothorax, the spider's legs become immobile and curl up.
Spiders may generate up to eight times their resting pressure. They can even jump up to 50 times their length by rapidly boosting blood pressure in the third and fourth pairs of legs. Because spiders lack antennae, they rely on their front pair of legs for sensory functions. Furthermore, the spider's limbs have evolved over millions of years, allowing it to survive certain attacks. They can scale a variety of surfaces at severe angles, allowing them to climb.

Advantages of having 8 Legs
Spiders use their limbs to strike and pin their prey while delivering poison through their fangs, in addition to walking. Some scholars assume that the evolution of eight legs is related to evading assailants rather than movement. To counter-attack or scare predators, certain spiders employ their limbs as a defensive strategy, raising and spreading their front legs.

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