“Spiders are insects.”

It's a common misconception to group all small, multi-legged creatures together, and this often leads to the mistaken belief that spiders are insects. This everyday classification likely originates from their shared characteristics as small, terrestrial arthropods that frequently inhabit similar environments, making it easy for the casual observer to overlook the more precise biological distinctions.

However, from a scientific standpoint, spiders and insects belong to entirely different classes within the phylum Arthropoda. Spiders are members of the class Arachnida, a group defined by several key anatomical features. These include having eight legs, a body divided into two main segments—a fused head and thorax called a cephalothorax, and an abdomen—and notably, no antennae. In contrast, insects belong to the class Insecta, which is characterized by having six legs, three distinct body segments (head, thorax, and abdomen), and a prominent pair of antennae.

The persistence of this belief often stems from a general lack of detailed biological knowledge among the public. While most people can readily identify a spider or an ant, the specific criteria used by scientists to classify these creatures are not widely known. The superficial similarities, such as their size and general appearance as "bugs," overshadow the fundamental differences in leg count, body segmentation, and sensory appendages, thus allowing the misconception to continue.