The class Arachnida includes a diverse group of arthropods: spiders, scorpions, ticks, mites, harvestmen, and their cousins. Scientists describe over 75,000 species of arachnids, the majority of them spiders. Most arachnids are carnivorous, typically preying on insects, and terrestrial, living on land. Arachnids provide an important service, keeping insect populations under control. To be classified in the class Arachnida, an arthropod must have certain characteristics. Arachnid bodies are divided into two distinct regions, the cephalothorax and the abdomen. Four pairs of legs attach to the cephalothorax. Arachnids lack wings and antennae.
Arachnids, like insects, are arthropods. All animals in the phylum Arthropoda have exoskeletons, segmented bodies, and at least three pairs of legs. Other groups belonging to the phylum Arthropoda include: Insecta (insects), Crustacea (crabs), Chilopoda (centipedes) and Diplopoda (millipedes). |