Cyclocosmia or "trapdoor spider" is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of spider

Spider

Spiders are air-breathing arthropods that have eight legs, and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms...

s in the Ctenizidae family.

The abdomen of spiders in this genus is abruptly truncated and ends in a hardened disc which is strengthened by a system of ribs and grooves. They use this to clog the entrance of their 7 to 15 cm deep vertical burrows when threatened, a phenomenon called phragmosis

Phragmosis

Phragmosis is any method by which an animal defends itself in its burrow by using its own body as a barrier. An example can be seen in the mygalomorph spider Idiosoma nigrum , which protects itself in its burrow by positioning itself so as to block the burrow with its abdomen, which is unusually hard...

. Strong spines are located around the edge of the disc. The four spinnerets are found just anterior to it, with the posterior, retractable spinnerets particularly large. C. ricketti females are 28 mm long, with a disc diameter of 16 mm. Only the bottom portion of the burrow is silk lined.

The individual species are separated from each other by the pattern of the abdominal disc, the number of hairs on its seam, and the shape of the spermatheca

Spermatheca

The spermatheca , also called receptaculum seminis , is an organ of the female reproductive tract in insects, some molluscs, oligochaeta worms and certain other invertebrates and vertebrates...

e.

Species

• Cyclocosmia lannaensis Schwendinger, 2005 — China
  China
  Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
  
  , Thailand
  Thailand
  Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...
  
  
• Cyclocosmia latusicosta Zhu, Zhang & Zhang, 2006 — China
• Cyclocosmia loricata (C. L. Koch, 1842) — Mexico
  Mexico
  The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
  
  , Guatemala
  Guatemala
  Guatemala is a country in Central America bordered by Mexico to the north and west, the Pacific Ocean to the southwest, Belize to the northeast, the Caribbean to the east, and Honduras and El Salvador to the southeast...
  
  
• Cyclocosmia ricketti (Pocock, 1901) — China
• Cyclocosmia siamensis Schwendinger, 2005 — Thailand
• Cyclocosmia torreya Gertsch & Platnick, 1975 — USA
• Cyclocosmia truncata (Hentz, 1841) — USA

Further reading

(2005): Two new Cyclocosmia (Araneae: Ctenizidae) from Thailand. Revue Suisse de Zoologie 112(1): 225-252

External links

• Cyclocosmia at Bugguide.net
• Cyclocosmia close up