The Class Arachnida includes spiders, scorpions, ticks, mites, and related organisms. Arachnids are arthropods with eight legs, two main body segments (cephalothorax and abdomen), and no antennae. Most are predators or parasites, using fangs, stingers, or specialized mouthparts to capture prey. They are found in nearly all terrestrial habitats and play important roles in ecosystems as predators, controlling insect populations and sometimes serving as vectors for disease.