[arthro- + podo-]
A phylum of invertebrate animals marked by bilateral symmetry, a hard exoskeleton, segmented bodies, and jointed paired appendages. It includes the crustaceans, insects, myriapods, arachnids, and similar forms. It is the largest animal phylum, containing over 900,000 species. Many are of medical importance because of their bites or stings, as parasites, and as vectors of microbial diseases.