Cyclocosmia ricketti, commonly known as the Chinese hourglass spider or Money trapdoor spider, is a rare species of trapdoor spider native to China. It is most famous for its extraordinary "truncated" abdomen, which ends in a hardened, patterned disk that many compare to an ancient coin, an Aztec seal, or even an Oreo cookie. 
 
Unique Characteristics and Behavior
Phragmosis (Burrow Defense): This spider uses its hardened abdominal disk as a living shield. When threatened, it crawls headfirst into its vertical burrow (typically 7–15 cm deep) and uses the disk to plug the entrance, making it nearly impossible for predators to enter.
Appearance: The abdomen appears "cut off" at the end. The disk is marked with a system of ribs and grooves; C. ricketti specifically has between 23 and 33 radiating ribs on each side.
Size: Females are typically larger, reaching about 25–30 mm in length, while males are around 20 mm.
Diet: They are nocturnal ambush predators. They wait at the entrance of their burrows for small insects to pass by, then strike with lightning speed. 
 
Habitat and Distribution
Range: Native to China, specifically found in provinces like Fujian, Zhejiang, and Sichuan.
Environment: They typically live in caves or hilly, undisturbed woods, often near stream banks where the soil is suitable for digging stable burrows.
Rarity: They are considered very rare; for example, only six specimens were officially recorded between the years 2000 and 2016. 
 
Human Interaction
Venom: Their bite is considered low-risk and non-toxic to humans, though it can still be painful.
Cultural History: The spider is believed to be described in ancient Chinese texts like the Erya (3rd century BC) as the diedang.