Editing Cercus (section)

{{Short description|Paired appendages on the rear-most segments of many arthropods}}
{{distinguish|circus}}
[[Image:Forficula auricularia.jpg|right|thumb|upright|[[Earwig]] with large cerci (top)]]
'''Cerci''' ({{singular}}: '''cercus''') are paired [[appendage]]s usually on the rear-most segments of many [[arthropod]]s, including [[insect]]s and [[symphyla]]ns. Many forms of cerci serve as sensory organs, but some serve as pinching weapons or as organs of [[copulation (zoology)|copulation]].<ref name="Tiegs"/> In many insects, they simply may be functionless [[vestigial structure]]s.

In basal arthropods, such as [[silverfish]], the cerci originate from the eleventh abdominal segment. As segment eleven is reduced or absent in the majority of arthropods, in such cases, the cerci emerge from the tenth abdominal segment.<ref name="UMN">{{cite web|url=http://www.entomology.umn.edu/museum/projects/Interactive_Keys/Intro_tutorial/GLOSSARY/Cerci.html|title=CERCI AND TERMINAL FILAMENT|work=Entomological Glossary|publisher=University of Minnesota|access-date=3 June 2014|url-status=dead|archive-url=https://web.archive.org/web/20120225054533/http://www.entomology.umn.edu/museum/projects/Interactive_Keys/Intro_tutorial/GLOSSARY/Cerci.html|archive-date=25 February 2012}}</ref> It is not clear that other structures so named are [[Homology (biology)|homologous]]. In the [[Symphyla]] they are associated with spinnerets.<ref name="Tiegs">{{cite journal |last1=Tiegs |first1=O. W. |title=Memoirs: The Post-Embryonic Development of Hanseniella Agilis (Symphyla) |journal=Journal of Cell Science |date=1 March 1945 |volume=s2-85 |issue=338 |pages=191–328 |doi=10.1242/jcs.s2-85.338.191 }}</ref>