Cercus

Not to be confused with circus.
Earwig with large cerci (top)

Cerci (sg.: cercus) are paired appendages usually on the rear-most segments of many arthropods, including insects and symphylans. Many forms of cerci serve as sensory organs, but some serve as pinching weapons or as organs of copulation.[1] In many insects, they simply may be functionless vestigial structures.

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.[2] It is not clear that other structures so named are homologous. In the Symphyla they are associated with spinnerets.[1]

  1. ^ a b Tiegs, O. W. (1 March 1945). "Memoirs: The Post-Embryonic Development of Hanseniella Agilis (Symphyla)". Journal of Cell Science. s2-85 (338): 191–328. doi:10.1242/jcs.s2-85.338.191.
  2. ^ "CERCI AND TERMINAL FILAMENT". Entomological Glossary. University of Minnesota. Archived from the original on 25 February 2012. Retrieved 3 June 2014.