Arachnids include spiders, scorpions, mites, and ticks. They all have eight legs. Spiders live anywhere that there are insects to eat. Some spiders spin webs to catch their prey. The trapdoor spider makes a tunnel in the ground and lines it with silk. The spider waits for an insect and opens its door to catch the prey. They use long teeth, called fangs to kill or stun their prey.