Do Spiders Have Bones?

Spiders do not have bones. They are arthropods, and like all such organisms, they have external skeletons that are the primary support for their muscles. Their exoskeletons consist of cuticles with joints in the surface that allow them to move.

The cuticle of a spider is made up of four layers. Insects, in contrast, have cuticles with only three layers. The cuticles of both spiders and insects consist of a mixture of protein and chitin fibers. Spiders do have a limited internal skeleton, but it is not made up of bone. This small endoskeleton contains collagen and consists of plates that do not articulate with one another the way that bones in the vertebrate skeleton do.