Arthropods are invertebrates, that is, they have no backbone, and rely instead on an external covering called an exoskeleton.
Arthropods range in size from microscopic to several inches in length.
Nearly every soil is home to many different arthropod species. Certain row-crop soils contain several dozen species of arthropods in a square mile. Several thousand different species may live in a square mile of forest soil. Arthropods can be grouped as shredders, predators, herbivores, and fungal-feeders, based on their functions in soil. Most soil-dwelling arthropods eat fungi, worms, or other arthropods.