Invertebrates are animals having no backbone or spinal column such as insects, mollusks, crustaceans, worms, and similar organisms. Invertebrates inhabit aquatic environments including freshwater and marine habitats, as well as terrestrial habitats on land.

Invertebrates depending on freshwater ecosystems such as lakes, rivers, streams and ponds are called freshwater invertebrates. Invertebrates that do not depend on aquatic ecosystems to complete any phase of their life cycle are called terrestrial invertebrates, living entirely on land. Common groups of invertebrates found in the southeastern U.S. are listed below.

Invertebrates of the Southeastern United States
Please note: the list below is not a complete list of regional invertebrate groups. It lists the region's common invertebrate groups (phyla) with examples of typical organisms.

Arthropods
Invertebrates belonging to the largest phylum of animals, Arthropoda, with an exoskeleton, segmented bodies, and jointed appendages, including many subphyla and classes, such as insects, crustaceans, horseshoe crabs, sea spiders, centipedes, millipedes, and the extinct trilobites.

Arachnids
Carnivorous arthropods, chiefly terrestrial, of the class Arachnida including spiders, scorpions, mites, ticks, false scorpions, palpigrades, solifugids, and harvestmen.

Crustaceans
Arthropods of class Crustacea, such as crabs, lobsters, shrimp, prawns, or barnacles, with hard shells (exoskeleton) and segmented bodies with pairs of jointed appendages.

Insects
Small arthropod animals of the class Insecta with bodies in 3 segments (head, thorax, and abdomen). They have 3 pairs of legs, 2 antennae, and usually one or two pairs of wings. Includes flies, mosquitoes, beetles, butterflies, bees, crickets, and dragonflies.

Mollusks
Invertebrates belonging to the phylum Mollusca with soft, nonsegmented bodies, often covered by a hard shell. Includes snails, clams, oysters, whelks, mussels, slugs, octopuses, and squids.

Annelids
Members of the phylum Annelida, Annelids are segmented worms that inhabit marine and freshwater environments, in addition to terrestrial environments. Annelids include three different classes: polychaetes, oligochaetes, and hirudinea (leeches).