How many legs does a spider have?

Spiders are fascinating creatures distinguished by a specific number of limbs. These arthropods possess eight legs, a defining characteristic that places them in the class Arachnida, alongside other familiar animals like scorpions, ticks, and mites. This eight-legged structure is a key feature that sets them apart from insects, which typically have six legs.

Each of a spider's eight legs is a complex appendage composed of seven segments, all attached to the cephalothorax, which is the fused head and thorax region of its body. Interestingly, spiders extend their legs not through opposing muscles like humans do, but primarily through hydraulic pressure. They pump a fluid called hemolymph into their legs, which causes them to straighten. When a spider dies, this pressure is lost, which is why their legs often curl inward.

Beyond their eight walking legs, spiders also have two additional appendages called pedipalps, located near their mouthparts. While these can sometimes resemble a small, extra pair of legs, they are not used for walking. Instead, pedipalps serve various functions such as sensing their environment, manipulating prey, and in male spiders, for transferring sperm during reproduction. This unique anatomy, including two main body segments and the absence of antennae or wings, clearly differentiates spiders from insects.