Many people have a strong aversion to things with more than four legs. This one trait alone shouldn't put an animal on the "yuck" list. Insects and spiders belong to a group of animals called arthropods, which simply means "jointed feet". The number of legs is a big distinguishing characteristic in this group. Six legs differentiate the insects, and eight legs are found on the spiders. The other important difference is the number of body parts on the animal. Insects have three: head, thorax, and abdomen. Spiders have only two: the cephalothorax and abdomen.