A scanning electron micrograph of the head of an arthropod, magnified x18. An arthropod is a member of a phylum of of invertebrate animals that includes insects, arachnids (spiders and mites), and crustaceans (crabs, lobsters, pillbugs, shrimp, etc.). They are members of the phylum Arthropoda and are characterised by having exoskeletons and jointed appendages. The word arthropod comes from the Greek words arthron (joint) and podos (foot). The family Formicidae, ants, is a group of social Hymenoptera among whom the worker is apterous, wingless. Also, ants have geniculate antennae and their abdominal pedicels have one or two segments.
