Cookie Cutter Spider

Cyclocosmia ricketti — the cookie cutter spider, also called the disc-rear or coin-rear spider — is one of the most extraordinarily-adapted spiders in the world and the textbook example of phragmosis (the use of body parts as living doors) in arachnids. The species is one of about 10 species in genus Cyclocosmia (family Halonoproctidae, the trapdoor spiders) and is endemic to montane forest of southern China and Vietnam. Adults are 25-35 mm body length with the unmistakable defining feature: the dorsal rear of the abdomen is FLATTENED into a hardened disc-shaped plate marked with intricate radiating ridges, grooves, and concentric circles that closely resemble a stamped coin or a pressed butter cookie. The disc is composed of thickened cuticle reinforced with internal sclerotized struts and is essentially a portable shield. The species lives in vertical burrows excavated in soft forest soil, lined with silk and capped at the top with a thin silk-and-soil door. When threatened by an attempted predator (typically wasps in the family Pompilidae that hunt trapdoor spiders), the spider retreats deep into the burrow and orients her body so that the disc-shaped abdomen blocks the burrow tunnel from below — presenting the predator with what appears to be a small carved coin or fungus body sitting in a hole, with no actual spider visible. The behavior is called 'phragmosis' (Greek 'phragmos' = barrier or fence) and is one of the most extreme body-as-armor adaptations in spiders. The disc is so detailed and so intricately marked that early Chinese spider collectors in the 19th century believed the disc patterns were artificially carved by craftsmen. Modern microscopy confirms the disc is naturally formed by the species during normal cuticle development. The species is one of the most-photographed Asian spiders in macro nature photography because of the extraordinary visual impact of the abdomen disc.