Invertebrates—animals without a backbone—make up most of the animal kingdom. West Virginia is home to thousands of species. We have freshwater jellyfish in the Ohio River and ponds and worms of all kinds. Flatworms are small, flat, and often found in streams. Roundworms are mostly microscopic, unseen parasites, like the one that causes heartworm in dogs. Segmented invertebrates include earthworms, which are vital for healthy soil and make for great fish bait. Leeches are mostly aquatic parasites that thrive off fish and reptiles but not mammals.

Snails carry a spiral shell and glide on a trail of mucus. Slugs are just snails without shells.

Mussels (freshwater clams) have two shells and gather food by filtering water. Mussels are highly endangered in West Virginia due to pollution and invasive species.

Arthropods are a huge group defined by their external skeleton (exoskeleton) and jointed legs. This group includes insects (six legs), spiders (arachnids, eight legs), millipedes, and centipedes.