What are the differences between insects and spiders?
Spiders and Insects have been separate independent linages of animals for 500 million years. Spiders have two body parts (cephalothorax and abdomen), while insects have 3 (head, thorax and abdomen). Besides the differences in number of legs, spiders and insects have different forms of respiration, different mouthparts, and different exoskeletons. Insects have antennae, while spiders don't. In short, spiders and insects are more different from one another than mice are from sharks.