What distinguishes spiders from insects?

Spiders are classified as arachnids, and one of their defining characteristics is the presence of eight legs. This is a key distinction between arachnids and insects, which typically have six legs. The eight-legged structure of spiders is adapted for various functions, including hunting, climbing, and web construction.

Insects, on the other hand, have three main body segments (head, thorax, abdomen) and undergo either complete or incomplete metamorphosis, which are processes involving developmental changes after hatching from eggs. Spiders do not undergo these types of metamorphosis, as they generally hatch from eggs as miniature versions of adults, without a distinct larval stage. Additionally, spiders have only two main body segments (the cephalothorax and abdomen), which further differentiates them from insects.

The possession of eight legs is a fundamental characteristic that clearly sets spiders apart from insects, reinforcing their classification in a separate order within the animal kingdom.