An arthropod is an invertebrate animal having an exoskeleton (external skeleton), a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda and include the insects, arachnids, crustaceans, and others. Arthropods are characterized by their jointed limbs and cuticles. There are many strange and beautiful arthropods. Most belong to one of three major groups: insects, crustaceans, or arachnids.Insects have six legs. They are the only arthropods capable of powered flight. like Dragonflies. Arachnids have eight legs. Spiders are, perhaps, the best-known arachnid. Crustaceans have ten or more legs. Most are aquatic, which means they live in water. Most aquatic crustaceans - crabs, lobsters, and shrimp - live in the sea.