What characteristic is unique to arachnids?

Arachnids are unique in their anatomy because they possess four pairs of legs, totaling eight legs. This characteristic distinguishes them from insects, which have six legs (three pairs), and other groups of arthropods. The four pairs of legs provide arachnids with a diverse range of movement and adaptability in their environments, whether they are hunting, climbing, or spinning webs.

In addition to their leg count, arachnids typically have two main body segments: the cephalothorax and the abdomen. This segmentation is another feature that sets them apart from insects, which have three body segments. Understanding this unique characteristic of arachnids helps in identifying and studying these organisms within the broader context of arachnology and entomology.