**Description:** Freshwater crustaceans with hard exoskeletons and powerful pincers; often called "Freshwater Lobsters."
**Size:** Typically 2 to 5 inches long depending on age and species.
**Sexual Dimorphism:** Males have larger, more robust pincers and specialized legs (gonopods) for reproduction located behind the walking legs.
**Behavior:** Highly sensitive to water pollution; their presence is a sign of high water quality. They swim backward rapidly by snapping their tails.
**Habitat:** Found under flat rocks in clean, flowing mountain streams and the reservoir bottom.