Cercus

Most cerci are segmented and jointed, or filiform (threadlike), but some take very different forms. Some Diplura, in particular Japyx species, have large, stout forcipate (pincer-like) cerci that they use in capturing their prey. The Dermaptera, or earwigs, are well known for the forcipate cerci that most of them bear, though species in the suborders Arixeniina and Hemimerina do not. It is not clear how many of the Dermaptera use their cerci for anything but defense, but some definitely feed on prey caught with the cerci, much as the Japygidae do. Some hexapods such as mayflies, silverfish and diplurans possess an accompanying third central tail filament which extends from the tip of the abdomen. This is referred to as the terminal filament and is not regarded as a cercus. Aphids have tube-like cornicles or siphunculi that are sometimes mistaken for cerci but are not morphologically related to cerci. ==Evolutionary origin==

Like many insect body parts, including mandibles, antennae and stylets, cerci are thought to have evolved from what were legs on the primal insect form, ==Gallery==

File:Pamphagidae Hoplolopha abdomen cerci IMG 0862s.JPG|Short cerci on abdomen of a species of pamphagid grasshopper File:Lepismatidae Ctenolepisma longicaudata 9815s.jpg|Long sensory cerci on Ctenolepisma, flanking the median cerciform appendage and paired stylets File:Diplura Campodea Japyx.jpg|Two forms of Diplura, illustrating cerci with sensory glandular function, as contrasted with forcipate forms of cerci used in predation ==References==