Cerci

Definition

Paired, segmented appendages arising from the terminal abdominal segments of many insects and some other arthropods, typically serving sensory functions (mechanoreception, chemoreception, or proprioception) and occasionally modified for grasping, defense, or clasping. Cerci are primitively present in most insect orders but are reduced or lost in many derived groups; they are homologous with similar structures in some non-insect hexapods.

Etymology

From Latin cercus, 'tail' or 'tuft at the end of a rope,' referring to their terminal position on the abdomen.

Example

In earwigs (Dermaptera), the cerci are enlarged and sclerotized into prominent forceps-like pincers used in defense, prey capture, and intraspecific combat, while in crickets (Orthoptera: Gryllidae), the long, filamentous cerci detect air currents and low-frequency vibrations to sense approaching predators.

Synonyms

• caudal appendages

Related Terms

• Epiproct
• paraproct
• Pygidium
• uropod
• Telson
• abdominal segment
• mechanoreceptor
• earwig
• Silverfish

Usage Notes

Cerci are distinct from the median terminal filament (epiproct) found in some primitive insects; they are always paired and lateral, never single or median. The term is sometimes loosely applied to superficially similar terminal appendages in non-hexapod arthropods (e.g., some crustacean uropods), but strict usage reserves 'cerci' for hexapods. In taxonomic descriptions, cercal morphology (shape, segmentation, setation) is often diagnostic, particularly within Dermaptera and Embioptera. Do not confuse with 'cercus' in plant morphology, where it refers to a lobe or appendage of a leaf base.